Introduce a DB color type

Represents `Label#color` as a `Gitlab::Color`, which is a domain
object for a hex color.

app/helpers/labels_helper.rb

@@ -61,7 +61,7 @@ module LabelsHelper
     render_label_text(
       label.name,
       suffix: suffix,
-      css_class: "gl-label-text #{text_color_class_for_bg(label.color)}",
+      css_class: "gl-label-text #{label.text_color_class}",
       bg_color: label.color
     )
   end
@@ -114,30 +114,8 @@ module LabelsHelper
     end
   end
 
-  def text_color_class_for_bg(bg_color)
-    if light_color?(bg_color)
-      'gl-label-text-dark'
-    else
-      'gl-label-text-light'
-    end
-  end
-
   def text_color_for_bg(bg_color)
-    if light_color?(bg_color)
-      '#333333'
-    else
-      '#FFFFFF'
-    end
-  end
-
-  def light_color?(color)
-    if color.length == 4
-      r, g, b = color[1, 4].scan(/./).map { |v| (v * 2).hex }
-    else
-      r, g, b = color[1, 7].scan(/.{2}/).map(&:hex)
-    end
-
-    (r + g + b) > 500
+    ::Gitlab::Color.of(bg_color).contrast
   end
 
   def labels_filter_path_with_defaults(only_group_labels: false, include_ancestor_groups: true, include_descendant_groups: false)

app/models/label.rb

@@ -12,8 +12,9 @@ class Label < ApplicationRecord
 
   cache_markdown_field :description, pipeline: :single_line
 
-  DEFAULT_COLOR = '#6699cc'
+  DEFAULT_COLOR = ::Gitlab::Color.of('#6699cc')
 
+  attribute :color, ::Gitlab::Database::Type::Color.new
   default_value_for :color, DEFAULT_COLOR
 
   has_many :lists, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
@@ -22,9 +23,9 @@ class Label < ApplicationRecord
   has_many :issues, through: :label_links, source: :target, source_type: 'Issue'
   has_many :merge_requests, through: :label_links, source: :target, source_type: 'MergeRequest'
 
-  before_validation :strip_whitespace_from_title_and_color
+  before_validation :strip_whitespace_from_title
 
-  validates :color, color: true, allow_blank: false
+  validates :color, color: true, presence: true
 
   # Don't allow ',' for label titles
   validates :title, presence: true, format: { with: /\A[^,]+\z/ }
@@ -212,7 +213,7 @@ class Label < ApplicationRecord
   end
 
   def text_color
-    LabelsHelper.text_color_for_bg(self.color)
+    color.contrast
   end
 
   def title=(value)
@@ -285,8 +286,8 @@ class Label < ApplicationRecord
     CGI.unescapeHTML(Sanitize.clean(value.to_s))
   end
 
-  def strip_whitespace_from_title_and_color
-    %w(color title).each { |attr| self[attr] = self[attr]&.strip }
+  def strip_whitespace_from_title
+    self[:title] = title&.strip
   end
 end
 

app/presenters/label_presenter.rb

@@ -14,6 +14,10 @@ class LabelPresenter < Gitlab::View::Presenter::Delegated
     end
   end
 
+  def text_color_class
+    "gl-label-text-#{label.color.contrast.luminosity}"
+  end
+
   def destroy_path
     case label
     when GroupLabel then group_label_path(label.group, label)

app/serializers/analytics/cycle_analytics/stage_entity.rb

@@ -57,7 +57,8 @@ module Analytics
       def html_description(event)
         options = {}
         if event.label_based?
-          options[:label_html] = render_label(event.label, link: '', small: true, tooltip: true)
+          label = event.label.present
+          options[:label_html] = render_label(label, link: '', small: true, tooltip: true)
         end
 
         content_tag(:p) { event.html_description(options).html_safe }

app/serializers/label_entity.rb

@@ -4,7 +4,9 @@ class LabelEntity < Grape::Entity
   expose :id
 
   expose :title
-  expose :color
+  expose :color do |label|
+    label.color.to_s
+  end
   expose :description
   expose :group_id
   expose :project_id

app/services/labels/base_service.rb

@@ -2,162 +2,8 @@
 
 module Labels
   class BaseService < ::BaseService
-    COLOR_NAME_TO_HEX = {
-      black: '#000000',
-      silver: '#C0C0C0',
-      gray: '#808080',
-      white: '#FFFFFF',
-      maroon: '#800000',
-      red: '#FF0000',
-      purple: '#800080',
-      fuchsia: '#FF00FF',
-      green: '#008000',
-      lime: '#00FF00',
-      olive: '#808000',
-      yellow: '#FFFF00',
-      navy: '#000080',
-      blue: '#0000FF',
-      teal: '#008080',
-      aqua: '#00FFFF',
-      orange: '#FFA500',
-      aliceblue: '#F0F8FF',
-      antiquewhite: '#FAEBD7',
-      aquamarine: '#7FFFD4',
-      azure: '#F0FFFF',
-      beige: '#F5F5DC',
-      bisque: '#FFE4C4',
-      blanchedalmond: '#FFEBCD',
-      blueviolet: '#8A2BE2',
-      brown: '#A52A2A',
-      burlywood: '#DEB887',
-      cadetblue: '#5F9EA0',
-      chartreuse: '#7FFF00',
-      chocolate: '#D2691E',
-      coral: '#FF7F50',
-      cornflowerblue: '#6495ED',
-      cornsilk: '#FFF8DC',
-      crimson: '#DC143C',
-      darkblue: '#00008B',
-      darkcyan: '#008B8B',
-      darkgoldenrod: '#B8860B',
-      darkgray: '#A9A9A9',
-      darkgreen: '#006400',
-      darkgrey: '#A9A9A9',
-      darkkhaki: '#BDB76B',
-      darkmagenta: '#8B008B',
-      darkolivegreen: '#556B2F',
-      darkorange: '#FF8C00',
-      darkorchid: '#9932CC',
-      darkred: '#8B0000',
-      darksalmon: '#E9967A',
-      darkseagreen: '#8FBC8F',
-      darkslateblue: '#483D8B',
-      darkslategray: '#2F4F4F',
-      darkslategrey: '#2F4F4F',
-      darkturquoise: '#00CED1',
-      darkviolet: '#9400D3',
-      deeppink: '#FF1493',
-      deepskyblue: '#00BFFF',
-      dimgray: '#696969',
-      dimgrey: '#696969',
-      dodgerblue: '#1E90FF',
-      firebrick: '#B22222',
-      floralwhite: '#FFFAF0',
-      forestgreen: '#228B22',
-      gainsboro: '#DCDCDC',
-      ghostwhite: '#F8F8FF',
-      gold: '#FFD700',
-      goldenrod: '#DAA520',
-      greenyellow: '#ADFF2F',
-      grey: '#808080',
-      honeydew: '#F0FFF0',
-      hotpink: '#FF69B4',
-      indianred: '#CD5C5C',
-      indigo: '#4B0082',
-      ivory: '#FFFFF0',
-      khaki: '#F0E68C',
-      lavender: '#E6E6FA',
-      lavenderblush: '#FFF0F5',
-      lawngreen: '#7CFC00',
-      lemonchiffon: '#FFFACD',
-      lightblue: '#ADD8E6',
-      lightcoral: '#F08080',
-      lightcyan: '#E0FFFF',
-      lightgoldenrodyellow: '#FAFAD2',
-      lightgray: '#D3D3D3',
-      lightgreen: '#90EE90',
-      lightgrey: '#D3D3D3',
-      lightpink: '#FFB6C1',
-      lightsalmon: '#FFA07A',
-      lightseagreen: '#20B2AA',
-      lightskyblue: '#87CEFA',
-      lightslategray: '#778899',
-      lightslategrey: '#778899',
-      lightsteelblue: '#B0C4DE',
-      lightyellow: '#FFFFE0',
-      limegreen: '#32CD32',
-      linen: '#FAF0E6',
-      mediumaquamarine: '#66CDAA',
-      mediumblue: '#0000CD',
-      mediumorchid: '#BA55D3',
-      mediumpurple: '#9370DB',
-      mediumseagreen: '#3CB371',
-      mediumslateblue: '#7B68EE',
-      mediumspringgreen: '#00FA9A',
-      mediumturquoise: '#48D1CC',
-      mediumvioletred: '#C71585',
-      midnightblue: '#191970',
-      mintcream: '#F5FFFA',
-      mistyrose: '#FFE4E1',
-      moccasin: '#FFE4B5',
-      navajowhite: '#FFDEAD',
-      oldlace: '#FDF5E6',
-      olivedrab: '#6B8E23',
-      orangered: '#FF4500',
-      orchid: '#DA70D6',
-      palegoldenrod: '#EEE8AA',
-      palegreen: '#98FB98',
-      paleturquoise: '#AFEEEE',
-      palevioletred: '#DB7093',
-      papayawhip: '#FFEFD5',
-      peachpuff: '#FFDAB9',
-      peru: '#CD853F',
-      pink: '#FFC0CB',
-      plum: '#DDA0DD',
-      powderblue: '#B0E0E6',
-      rosybrown: '#BC8F8F',
-      royalblue: '#4169E1',
-      saddlebrown: '#8B4513',
-      salmon: '#FA8072',
-      sandybrown: '#F4A460',
-      seagreen: '#2E8B57',
-      seashell: '#FFF5EE',
-      sienna: '#A0522D',
-      skyblue: '#87CEEB',
-      slateblue: '#6A5ACD',
-      slategray: '#708090',
-      slategrey: '#708090',
-      snow: '#FFFAFA',
-      springgreen: '#00FF7F',
-      steelblue: '#4682B4',
-      tan: '#D2B48C',
-      thistle: '#D8BFD8',
-      tomato: '#FF6347',
-      turquoise: '#40E0D0',
-      violet: '#EE82EE',
-      wheat: '#F5DEB3',
-      whitesmoke: '#F5F5F5',
-      yellowgreen: '#9ACD32',
-      rebeccapurple: '#663399'
-    }.freeze
-
     def convert_color_name_to_hex
-      color = params[:color]
-      color_name = color.strip.downcase
-
-      return color if color_name.start_with?('#')
-
-      COLOR_NAME_TO_HEX[color_name.to_sym] || color
+      ::Gitlab::Color.of(params[:color])
     end
   end
 end

app/validators/color_validator.rb

@@ -12,11 +12,13 @@
 #   end
 #
 class ColorValidator < ActiveModel::EachValidator
-  PATTERN = /\A\#(?:[0-9A-Fa-f]{3}){1,2}\Z/.freeze
-
   def validate_each(record, attribute, value)
-    unless value =~ PATTERN
-      record.errors.add(attribute, "must be a valid color code")
+    case value
+    when NilClass        then return
+    when ::Gitlab::Color then return if value.valid?
+    when ::String        then return if ::Gitlab::Color.new(value).valid?
     end
+
+    record.errors.add(attribute, "must be a valid color code")
   end
 end

ee/app/helpers/ee/labels_helper.rb

@@ -13,11 +13,11 @@ module EE
 
       render_label_text(
         label.scoped_label_key,
-        css_class: "gl-label-text #{text_color_class_for_bg(label.color)}",
+        css_class: "gl-label-text #{label.text_color_class}",
         bg_color: label.color
       ) + render_label_text(
         label.scoped_label_value,
-        css_class: "gl-label-text-scoped #{('gl-label-text-dark' if light_color?(label.color))}",
+        css_class: "gl-label-text-scoped #{label.text_color_class}",
         suffix: suffix
       )
     end

ee/spec/lib/bulk_imports/groups/pipelines/epics_pipeline_spec.rb

@@ -61,7 +61,7 @@ RSpec.describe BulkImports::Groups::Pipelines::EpicsPipeline do
       expect(group.epics.first.labels.count).to eq(1)
       expect(label.title).to eq('title')
       expect(label.description).to eq('description')
-      expect(label.color).to eq('#cd2c5c')
+      expect(label.color).to be_color('#cd2c5c')
     end
 
     it 'imports epic system note metadata' do

ee/spec/lib/ee/gitlab/import_export/group/legacy_tree_restorer_spec.rb

@@ -51,7 +51,7 @@ RSpec.describe Gitlab::ImportExport::Group::LegacyTreeRestorer do
         expect(group.epics.first.labels.count).to eq(1)
         expect(label.title).to eq('title')
         expect(label.description).to eq('description')
-        expect(label.color).to eq('#cd2c5c')
+        expect(label.color).to be_color('#cd2c5c')
       end
     end
 

ee/spec/lib/ee/gitlab/import_export/group/legacy_tree_saver_spec.rb

@@ -107,7 +107,7 @@ RSpec.describe Gitlab::ImportExport::Group::LegacyTreeSaver do
         epic_label = epic_json['label_links'].first['label']
         expect(epic_label['title']).to eq(label.title)
         expect(epic_label['description']).to eq(label.description)
-        expect(epic_label['color']).to eq(label.color)
+        expect(epic_label['color']).to be_color(label.color)
       end
     end
 

ee/spec/lib/ee/gitlab/import_export/group/tree_restorer_spec.rb

@@ -59,7 +59,7 @@ RSpec.describe Gitlab::ImportExport::Group::TreeRestorer do
         expect(group.epics.first.labels.count).to eq(1)
         expect(label.title).to eq('title')
         expect(label.description).to eq('description')
-        expect(label.color).to eq('#cd2c5c')
+        expect(label.color).to be_color('#cd2c5c')
       end
     end
 

ee/spec/lib/ee/gitlab/import_export/group/tree_saver_spec.rb

@@ -105,7 +105,7 @@ RSpec.describe Gitlab::ImportExport::Group::TreeSaver do
         epic_label = epic_json['label_links'].first['label']
         expect(epic_label['title']).to eq(label.title)
         expect(epic_label['description']).to eq(label.description)
-        expect(epic_label['color']).to eq(label.color)
+        expect(epic_label['color']).to be_color(label.color)
       end
     end
 

ee/spec/services/security/auto_fix_label_service_spec.rb

@@ -32,7 +32,7 @@ RSpec.describe Security::AutoFixLabelService do
 
         expect(result).to be_success
         expect(label.title).to eq(title)
-        expect(label.color).to eq(color)
+        expect(label.color).to be_color(color)
         expect(label.description).to eq(description)
       end
     end

lib/api/entities/label_basic.rb

@@ -3,7 +3,11 @@
 module API
   module Entities
     class LabelBasic < Grape::Entity
-      expose :id, :name, :color, :description, :description_html, :text_color
+      expose :id, :name, :description, :description_html, :text_color
+
+      expose :color do |label, options|
+        label.color.to_s
+      end
     end
   end
 end

lib/gitlab/color.rb

+# frozen_string_literal: true
+
+module Gitlab
+  class Color
+    PATTERN = /\A\#(?:[0-9A-Fa-f]{3}){1,2}\Z/.freeze
+
+    def initialize(value)
+      @value = value&.strip&.freeze
+    end
+
+    module Constants
+      DARK = Color.new('#333333')
+      LIGHT = Color.new('#FFFFFF')
+
+      COLOR_NAME_TO_HEX = {
+        black: '#000000',
+        silver: '#C0C0C0',
+        gray: '#808080',
+        white: '#FFFFFF',
+        maroon: '#800000',
+        red: '#FF0000',
+        purple: '#800080',
+        fuchsia: '#FF00FF',
+        green: '#008000',
+        lime: '#00FF00',
+        olive: '#808000',
+        yellow: '#FFFF00',
+        navy: '#000080',
+        blue: '#0000FF',
+        teal: '#008080',
+        aqua: '#00FFFF',
+        orange: '#FFA500',
+        aliceblue: '#F0F8FF',
+        antiquewhite: '#FAEBD7',
+        aquamarine: '#7FFFD4',
+        azure: '#F0FFFF',
+        beige: '#F5F5DC',
+        bisque: '#FFE4C4',
+        blanchedalmond: '#FFEBCD',
+        blueviolet: '#8A2BE2',
+        brown: '#A52A2A',
+        burlywood: '#DEB887',
+        cadetblue: '#5F9EA0',
+        chartreuse: '#7FFF00',
+        chocolate: '#D2691E',
+        coral: '#FF7F50',
+        cornflowerblue: '#6495ED',
+        cornsilk: '#FFF8DC',
+        crimson: '#DC143C',
+        darkblue: '#00008B',
+        darkcyan: '#008B8B',
+        darkgoldenrod: '#B8860B',
+        darkgray: '#A9A9A9',
+        darkgreen: '#006400',
+        darkgrey: '#A9A9A9',
+        darkkhaki: '#BDB76B',
+        darkmagenta: '#8B008B',
+        darkolivegreen: '#556B2F',
+        darkorange: '#FF8C00',
+        darkorchid: '#9932CC',
+        darkred: '#8B0000',
+        darksalmon: '#E9967A',
+        darkseagreen: '#8FBC8F',
+        darkslateblue: '#483D8B',
+        darkslategray: '#2F4F4F',
+        darkslategrey: '#2F4F4F',
+        darkturquoise: '#00CED1',
+        darkviolet: '#9400D3',
+        deeppink: '#FF1493',
+        deepskyblue: '#00BFFF',
+        dimgray: '#696969',
+        dimgrey: '#696969',
+        dodgerblue: '#1E90FF',
+        firebrick: '#B22222',
+        floralwhite: '#FFFAF0',
+        forestgreen: '#228B22',
+        gainsboro: '#DCDCDC',
+        ghostwhite: '#F8F8FF',
+        gold: '#FFD700',
+        goldenrod: '#DAA520',
+        greenyellow: '#ADFF2F',
+        grey: '#808080',
+        honeydew: '#F0FFF0',
+        hotpink: '#FF69B4',
+        indianred: '#CD5C5C',
+        indigo: '#4B0082',
+        ivory: '#FFFFF0',
+        khaki: '#F0E68C',
+        lavender: '#E6E6FA',
+        lavenderblush: '#FFF0F5',
+        lawngreen: '#7CFC00',
+        lemonchiffon: '#FFFACD',
+        lightblue: '#ADD8E6',
+        lightcoral: '#F08080',
+        lightcyan: '#E0FFFF',
+        lightgoldenrodyellow: '#FAFAD2',
+        lightgray: '#D3D3D3',
+        lightgreen: '#90EE90',
+        lightgrey: '#D3D3D3',
+        lightpink: '#FFB6C1',
+        lightsalmon: '#FFA07A',
+        lightseagreen: '#20B2AA',
+        lightskyblue: '#87CEFA',
+        lightslategray: '#778899',
+        lightslategrey: '#778899',
+        lightsteelblue: '#B0C4DE',
+        lightyellow: '#FFFFE0',
+        limegreen: '#32CD32',
+        linen: '#FAF0E6',
+        mediumaquamarine: '#66CDAA',
+        mediumblue: '#0000CD',
+        mediumorchid: '#BA55D3',
+        mediumpurple: '#9370DB',
+        mediumseagreen: '#3CB371',
+        mediumslateblue: '#7B68EE',
+        mediumspringgreen: '#00FA9A',
+        mediumturquoise: '#48D1CC',
+        mediumvioletred: '#C71585',
+        midnightblue: '#191970',
+        mintcream: '#F5FFFA',
+        mistyrose: '#FFE4E1',
+        moccasin: '#FFE4B5',
+        navajowhite: '#FFDEAD',
+        oldlace: '#FDF5E6',
+        olivedrab: '#6B8E23',
+        orangered: '#FF4500',
+        orchid: '#DA70D6',
+        palegoldenrod: '#EEE8AA',
+        palegreen: '#98FB98',
+        paleturquoise: '#AFEEEE',
+        palevioletred: '#DB7093',
+        papayawhip: '#FFEFD5',
+        peachpuff: '#FFDAB9',
+        peru: '#CD853F',
+        pink: '#FFC0CB',
+        plum: '#DDA0DD',
+        powderblue: '#B0E0E6',
+        rosybrown: '#BC8F8F',
+        royalblue: '#4169E1',
+        saddlebrown: '#8B4513',
+        salmon: '#FA8072',
+        sandybrown: '#F4A460',
+        seagreen: '#2E8B57',
+        seashell: '#FFF5EE',
+        sienna: '#A0522D',
+        skyblue: '#87CEEB',
+        slateblue: '#6A5ACD',
+        slategray: '#708090',
+        slategrey: '#708090',
+        snow: '#FFFAFA',
+        springgreen: '#00FF7F',
+        steelblue: '#4682B4',
+        tan: '#D2B48C',
+        thistle: '#D8BFD8',
+        tomato: '#FF6347',
+        turquoise: '#40E0D0',
+        violet: '#EE82EE',
+        wheat: '#F5DEB3',
+        whitesmoke: '#F5F5F5',
+        yellowgreen: '#9ACD32',
+        rebeccapurple: '#663399'
+      }.stringify_keys.transform_values { Color.new(_1) }.freeze
+    end
+
+    def self.of(color)
+      raise ArgumentError, 'No color spec' unless color
+      return color if color.is_a?(self)
+
+      color = color.to_s.strip
+      Constants::COLOR_NAME_TO_HEX[color.downcase] || new(color)
+    end
+
+    def to_s
+      @value.to_s
+    end
+
+    def as_json(_options = nil)
+      to_s
+    end
+
+    def eql(other)
+      return false unless other.is_a?(self.class)
+
+      to_s == other.to_s
+    end
+    alias_method :==, :eql
+
+    def valid?
+      PATTERN.match?(@value)
+    end
+
+    def light?
+      valid? && rgb.sum > 500
+    end
+
+    def luminosity
+      return :light if light?
+
+      :dark
+    end
+
+    def contrast
+      return Constants::DARK if light?
+
+      Constants::LIGHT
+    end
+
+    private
+
+    def rgb
+      return [] unless valid?
+
+      @rgb ||= begin
+        if @value.length == 4
+          @value[1, 4].scan(/./).map { |v| (v * 2).hex }
+        else
+          @value[1, 7].scan(/.{2}/).map(&:hex)
+        end
+      end
+    end
+  end
+end

lib/gitlab/database/type/color.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Database
+    module Type
+      class Color < ActiveModel::Type::Value
+        def serialize(value)
+          value.to_s if value
+        end
+
+        def serializable?(value)
+          value.nil? || value.is_a?(::String) || value.is_a?(::Gitlab::Color)
+        end
+
+        def cast_value(value)
+          ::Gitlab::Color.new(value.to_s)
+        end
+      end
+    end
+  end
+end

spec/helpers/labels_helper_spec.rb

@@ -114,16 +114,16 @@ RSpec.describe LabelsHelper do
 
   describe 'text_color_for_bg' do
     it 'uses light text on dark backgrounds' do
-      expect(text_color_for_bg('#222E2E')).to eq('#FFFFFF')
+      expect(text_color_for_bg('#222E2E')).to be_color('#FFFFFF')
     end
 
     it 'uses dark text on light backgrounds' do
-      expect(text_color_for_bg('#EEEEEE')).to eq('#333333')
+      expect(text_color_for_bg('#EEEEEE')).to be_color('#333333')
     end
 
     it 'supports RGB triplets' do
-      expect(text_color_for_bg('#FFF')).to eq '#333333'
-      expect(text_color_for_bg('#000')).to eq '#FFFFFF'
+      expect(text_color_for_bg('#FFF')).to be_color '#333333'
+      expect(text_color_for_bg('#000')).to be_color '#FFFFFF'
     end
   end
 

spec/lib/banzai/filter/references/label_reference_filter_spec.rb

@@ -277,7 +277,7 @@ RSpec.describe Banzai::Filter::References::LabelReferenceFilter do
   end
 
   context 'References with html entities' do
-    let!(:label) { create(:label, name: '<html>', project: project) }
+    let!(:label) { create(:label, title: '<html>', project: project) }
 
     it 'links to a valid reference' do
       doc = reference_filter('See ~"<html>"')

spec/lib/bulk_imports/common/pipelines/labels_pipeline_spec.rb

@@ -43,7 +43,7 @@ RSpec.describe BulkImports::Common::Pipelines::LabelsPipeline do
 
       expect(label.title).to eq('Label 1')
       expect(label.description).to eq('Label 1')
-      expect(label.color).to eq('#6699cc')
+      expect(label.color).to be_color('#6699cc')
       expect(File.directory?(tmpdir)).to eq(false)
     end
   end

spec/lib/gitlab/color_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+RSpec.describe Gitlab::Color do
+  describe ".of" do
+    described_class::Constants::COLOR_NAME_TO_HEX.each do |name, value|
+      it "parses #{name} to #{value}" do
+        expect(described_class.of(name)).to eq(value)
+      end
+    end
+
+    it 'parses hex literals as colors' do
+      expect(described_class.of('#fff')).to eq(described_class.new('#fff'))
+      expect(described_class.of('#fefefe')).to eq(described_class.new('#fefefe'))
+    end
+
+    it 'raises if the input is nil' do
+      expect { described_class.of(nil) }.to raise_error(ArgumentError)
+    end
+
+    it 'returns an invalid color if the input is not valid' do
+      expect(described_class.of('unknown color')).not_to be_valid
+    end
+  end
+
+  describe '#new' do
+    it 'handles nil values' do
+      expect(described_class.new(nil)).to eq(described_class.new(nil))
+    end
+
+    it 'strips input' do
+      expect(described_class.new('  abc  ')).to eq(described_class.new('abc'))
+    end
+  end
+
+  describe '#valid?' do
+    described_class::Constants::COLOR_NAME_TO_HEX.each_key do |name|
+      specify "#{name} is a valid color" do
+        expect(described_class.of(name)).to be_valid
+      end
+    end
+
+    specify '#fff is a valid color' do
+      expect(described_class.new('#fff')).to be_valid
+    end
+
+    specify '#ffffff is a valid color' do
+      expect(described_class.new('#ffffff')).to be_valid
+    end
+
+    specify '#ABCDEF is a valid color' do
+      expect(described_class.new('#ABCDEF')).to be_valid
+    end
+
+    specify '#123456 is a valid color' do
+      expect(described_class.new('#123456')).to be_valid
+    end
+
+    specify '#1234567 is not a valid color' do
+      expect(described_class.new('#1234567')).not_to be_valid
+    end
+
+    specify 'fff is not a valid color' do
+      expect(described_class.new('fff')).not_to be_valid
+    end
+
+    specify '#deadbeaf is not a valid color' do
+      expect(described_class.new('#deadbeaf')).not_to be_valid
+    end
+
+    specify '#a1b2c3 is a valid color' do
+      expect(described_class.new('#a1b2c3')).to be_valid
+    end
+
+    specify 'nil is not a valid color' do
+      expect(described_class.new(nil)).not_to be_valid
+    end
+  end
+
+  describe '#light?' do
+    specify '#fff is light' do
+      expect(described_class.new('#fff')).to be_light
+    end
+
+    specify '#a7a7a7 is light' do
+      expect(described_class.new('#a7a7a7')).to be_light
+    end
+
+    specify '#a6a7a7 is dark' do
+      expect(described_class.new('#a6a7a7')).not_to be_light
+    end
+
+    specify '#000 is dark' do
+      expect(described_class.new('#000')).not_to be_light
+    end
+
+    specify 'invalid colors are not light' do
+      expect(described_class.new('not-a-color')).not_to be_light
+    end
+  end
+
+  describe '#contrast' do
+    context 'with light colors' do
+      it 'is dark' do
+        %w[#fff #fefefe #a7a7a7].each do |hex|
+          expect(described_class.new(hex)).to have_attributes(
+            contrast: described_class::Constants::DARK,
+            luminosity: :light
+          )
+        end
+      end
+    end
+
+    context 'with dark colors' do
+      it 'is light' do
+        %w[#000 #a6a7a7].each do |hex|
+          expect(described_class.new(hex)).to have_attributes(
+            contrast: described_class::Constants::LIGHT,
+            luminosity: :dark
+          )
+        end
+      end
+    end
+  end
+
+  describe 'as_json' do
+    it 'serializes correctly' do
+      expect(described_class.new('#f0f1f2').as_json).to eq('#f0f1f2')
+    end
+  end
+end

spec/lib/gitlab/database/type/color_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe ::Gitlab::Database::Type::Color do
+  subject(:type) { described_class.new }
+
+  let(:color) { ::Gitlab::Color.of('red') }
+
+  it 'serializes by calling #to_s' do
+    expect(type.serialize(color)).to eq(color.to_s)
+  end
+
+  it 'serializes nil to nil' do
+    expect(type.serialize(nil)).to be_nil
+  end
+
+  it 'casts by calling Color::new' do
+    expect(type.cast('#fff')).to eq(::Gitlab::Color.new('#fff'))
+  end
+
+  it 'accepts colors as arguments to cast' do
+    expect(type.cast(color)).to eq(color)
+  end
+
+  it 'allows nil database values' do
+    expect(type.cast(nil)).to be_nil
+  end
+
+  it 'tells us what is serializable' do
+    [nil, 'foo', color].each do |value|
+      expect(type.serializable?(value)).to be true
+    end
+  end
+
+  it 'tells us what is not serializable' do
+    [0, 3.2, true, Time.current, { some: 'hash' }].each do |value|
+      expect(type.serializable?(value)).to be false
+    end
+  end
+end

spec/models/label_spec.rb

@@ -67,24 +67,21 @@ RSpec.describe Label do
       label = described_class.new(color: '   #abcdef   ')
       label.valid?
 
-      expect(label.color).to eq('#abcdef')
+      expect(label.color).to be_color('#abcdef')
     end
 
     it 'uses default color if color is missing' do
       label = described_class.new(color: nil)
 
-      expect(label.color).to be(Label::DEFAULT_COLOR)
+      expect(label.color).to be_color(Label::DEFAULT_COLOR)
     end
   end
 
   describe '#text_color' do
     it 'uses default color if color is missing' do
-      expect(LabelsHelper).to receive(:text_color_for_bg).with(Label::DEFAULT_COLOR)
-        .and_return(spy)
-
       label = described_class.new(color: nil)
 
-      label.text_color
+      expect(label.text_color).to eq(Label::DEFAULT_COLOR.contrast)
     end
   end
 

spec/requests/api/group_labels_spec.rb

@@ -140,7 +140,7 @@ RSpec.describe API::GroupLabels do
 
       expect(response).to have_gitlab_http_status(:ok)
       expect(json_response['name']).to eq(group_label1.name)
-      expect(json_response['color']).to eq(group_label1.color)
+      expect(json_response['color']).to be_color(group_label1.color)
       expect(json_response['description']).to eq(group_label1.description)
     end
   end
@@ -156,7 +156,7 @@ RSpec.describe API::GroupLabels do
 
       expect(response).to have_gitlab_http_status(:created)
       expect(json_response['name']).to eq(valid_new_label_title)
-      expect(json_response['color']).to eq('#FFAABB')
+      expect(json_response['color']).to be_color('#FFAABB')
       expect(json_response['description']).to eq('test')
     end
 
@@ -169,7 +169,7 @@ RSpec.describe API::GroupLabels do
 
       expect(response).to have_gitlab_http_status(:created)
       expect(json_response['name']).to eq(valid_new_label_title)
-      expect(json_response['color']).to eq('#FFAABB')
+      expect(json_response['color']).to be_color('#FFAABB')
       expect(json_response['description']).to be_nil
     end
 
@@ -276,7 +276,7 @@ RSpec.describe API::GroupLabels do
 
       expect(response).to have_gitlab_http_status(:ok)
       expect(json_response['name']).to eq(valid_new_label_title)
-      expect(json_response['color']).to eq('#FFFFFF')
+      expect(json_response['color']).to be_color('#FFFFFF')
       expect(json_response['description']).to eq('test')
     end
 
@@ -332,7 +332,7 @@ RSpec.describe API::GroupLabels do
 
       expect(response).to have_gitlab_http_status(:ok)
       expect(json_response['name']).to eq(valid_new_label_title)
-      expect(json_response['color']).to eq('#FFFFFF')
+      expect(json_response['color']).to be_color('#FFFFFF')
       expect(json_response['description']).to eq('test')
     end
 

spec/requests/api/labels_spec.rb

@@ -34,7 +34,7 @@ RSpec.describe API::Labels do
 
         expect(response).to have_gitlab_http_status(:ok)
         expect(json_response['name']).to eq(valid_label_title_2)
-        expect(json_response['color']).to eq(label1.color)
+        expect(json_response['color']).to be_color(label1.color)
       end
 
       it "returns 200 if colors is changed (#{route_type} route)" do
@@ -42,7 +42,7 @@ RSpec.describe API::Labels do
 
         expect(response).to have_gitlab_http_status(:ok)
         expect(json_response['name']).to eq(label1.name)
-        expect(json_response['color']).to eq('#FFFFFF')
+        expect(json_response['color']).to be_color('#FFFFFF')
       end
 
       it "returns 200 if a priority is added (#{route_type} route)" do
@@ -86,7 +86,7 @@ RSpec.describe API::Labels do
 
         expect(response).to have_gitlab_http_status(:ok)
         expect(json_response['name']).to eq(valid_label_title_2)
-        expect(json_response['color']).to eq('#FFFFFF')
+        expect(json_response['color']).to be_color('#FFFFFF')
         expect(json_response['description']).to eq('test')
       end
 
@@ -266,8 +266,8 @@ RSpec.describe API::Labels do
                                                 'open_merge_requests_count' => 0,
                                                 'name' => group_label.name,
                                                 'description' => nil,
-                                                'color' => a_string_matching(/^#\h{6}$/),
-                                                'text_color' => a_string_matching(/^#\h{6}$/),
+                                                'color' => a_valid_color,
+                                                'text_color' => a_valid_color,
                                                 'priority' => nil,
                                                 'subscribed' => false,
                                                 'is_project_label' => false)
@@ -277,8 +277,8 @@ RSpec.describe API::Labels do
                                                    'open_merge_requests_count' => 1,
                                                    'name' => priority_label.name,
                                                    'description' => nil,
-                                                   'color' => a_string_matching(/^#\h{6}$/),
-                                                   'text_color' => a_string_matching(/^#\h{6}$/),
+                                                   'color' => a_valid_color,
+                                                   'text_color' => a_valid_color,
                                                    'priority' => 3,
                                                    'subscribed' => false,
                                                    'is_project_label' => true)
@@ -336,7 +336,7 @@ RSpec.describe API::Labels do
 
       expect(response).to have_gitlab_http_status(:created)
       expect(json_response['name']).to eq(valid_label_title_2)
-      expect(json_response['color']).to eq('#FFAABB')
+      expect(json_response['color']).to be_color('#FFAABB')
       expect(json_response['description']).to eq('test')
       expect(json_response['priority']).to eq(2)
     end
@@ -350,7 +350,7 @@ RSpec.describe API::Labels do
 
       expect(response).to have_gitlab_http_status(:created)
       expect(json_response['name']).to eq(valid_label_title_2)
-      expect(json_response['color']).to eq('#FFAABB')
+      expect(json_response['color']).to be_color('#FFAABB')
       expect(json_response['description']).to be_nil
       expect(json_response['priority']).to be_nil
     end
@@ -365,7 +365,7 @@ RSpec.describe API::Labels do
 
       expect(response).to have_gitlab_http_status(:created)
       expect(json_response['name']).to eq(valid_label_title_2)
-      expect(json_response['color']).to eq('#FFAABB')
+      expect(json_response['color']).to be_color('#FFAABB')
       expect(json_response['description']).to be_nil
       expect(json_response['priority']).to eq(3)
     end
@@ -552,7 +552,7 @@ RSpec.describe API::Labels do
 
       expect(response).to have_gitlab_http_status(:ok)
       expect(json_response['name']).to eq(label1.name)
-      expect(json_response['color']).to eq(label1.color)
+      expect(json_response['color']).to be_color(label1.color.to_s)
     end
 
     context 'if group label already exists' do

spec/serializers/label_serializer_spec.rb

@@ -40,7 +40,7 @@ RSpec.describe LabelSerializer do
         expect(subject.keys).to eq([:id, :title, :color, :project_id, :text_color])
         expect(subject[:id]).to eq(resource.id)
         expect(subject[:title]).to eq(resource.title)
-        expect(subject[:color]).to eq(resource.color)
+        expect(subject[:color]).to be_color(resource.color)
         expect(subject[:text_color]).to eq(resource.text_color)
         expect(subject[:project_id]).to eq(resource.project_id)
       end

spec/services/labels/create_service_spec.rb

@@ -14,7 +14,7 @@ RSpec.describe Labels::CreateService do
     let(:unknown_color) { 'unknown' }
     let(:no_color) { '' }
 
-    let(:expected_saved_color) { hex_color }
+    let(:expected_saved_color) { ::Gitlab::Color.of(hex_color) }
 
     context 'in a project' do
       context 'with color in hex-code' do
@@ -47,7 +47,6 @@ RSpec.describe Labels::CreateService do
       context 'with color surrounded by spaces' do
         it 'creates a label' do
           label = described_class.new(params_with(spaced_color)).execute(project: project)
-
           expect(label).to be_persisted
           expect(label.color).to eq expected_saved_color
         end

spec/services/labels/promote_service_spec.rb

@@ -202,7 +202,7 @@ RSpec.describe Labels::PromoteService do
 
           expect(new_label.title).to eq(promoted_label_name)
           expect(new_label.description).to eq(promoted_description)
-          expect(new_label.color).to eq(promoted_color)
+          expect(new_label.color).to be_color(promoted_color)
         end
 
         it_behaves_like 'promoting a project label to a group label'

spec/services/labels/update_service_spec.rb

@@ -13,7 +13,7 @@ RSpec.describe Labels::UpdateService do
     let(:unknown_color) { 'unknown' }
     let(:no_color) { '' }
 
-    let(:expected_saved_color) { hex_color }
+    let(:expected_saved_color) { ::Gitlab::Color.of(hex_color) }
 
     before do
       @label = Labels::CreateService.new(title: 'Initial', color: '#000000').execute(project: project)

spec/services/projects/create_service_spec.rb

@@ -23,11 +23,11 @@ RSpec.describe Projects::CreateService, '#execute' do
     end
 
     it 'creates labels on project creation' do
-      created_label = project.labels.last
-
-      expect(created_label.type).to eq('ProjectLabel')
-      expect(created_label.project_id).to eq(project.id)
-      expect(created_label.title).to eq('bug')
+      expect(project.labels).to include have_attributes(
+        type: eq('ProjectLabel'),
+        project_id: eq(project.id),
+        title: eq('bug')
+      )
     end
 
     context 'using gitlab project import' do

spec/support/matchers/be_color.rb

+# frozen_string_literal: true
+
+# Assert that this value is a valid color equal to the argument
+#
+# ```
+# expect(value).to be_color('#fff')
+# ```
+RSpec::Matchers.define :be_color do |expected|
+  match do |actual|
+    next false unless actual.present?
+
+    if expected
+      ::Gitlab::Color.of(actual) == ::Gitlab::Color.of(expected)
+    else
+      ::Gitlab::Color.of(actual).valid?
+    end
+  end
+end
+
+RSpec::Matchers.alias_matcher :a_valid_color, :be_color

spec/support/shared_examples/services/incident_shared_examples.rb

@@ -70,7 +70,7 @@ RSpec.shared_examples 'incident management label service' do
         expect(execute).to be_success
         expect(execute.payload).to eq(label: label)
         expect(label.title).to eq(title)
-        expect(label.color).to eq(color)
+        expect(label.color).to be_color(color)
         expect(label.description).to eq(description)
       end
     end

spec/validators/color_validator_spec.rb

@@ -23,7 +23,12 @@ RSpec.describe ColorValidator do
     '#ffff'      | false
     '#000111222' | false
     'invalid'    | false
+    'red'        | false
     '000'        | false
+    nil          | true # use presence to validate non-nil
+    ''           | false
+    Time.current | false
+    ::Gitlab::Color.of(:red) | true
   end
 
   with_them do
@@ -41,4 +46,22 @@ RSpec.describe ColorValidator do
       Timeout.timeout(5.seconds) { subject.valid? }
     end.not_to raise_error
   end
+
+  context 'when color must be present' do
+    subject do
+      Class.new do
+        include ActiveModel::Model
+        include ActiveModel::Validations
+        attr_accessor :color
+
+        validates :color, color: true, presence: true
+      end.new
+    end
+
+    it 'rejects nil' do
+      subject.color = nil
+
+      expect(subject).not_to be_valid
+    end
+  end
 end