rename theme to match actual colors

app/assets/stylesheets/framework/gitlab-theme.scss

@@ -99,10 +99,10 @@ $theme-graphite: #777;
 $theme-graphite-dark: #666;
 $theme-graphite-darker: #555;
 
-$theme-gray-light: #979797;
-$theme-gray: #373737;
-$theme-gray-dark: #272727;
-$theme-gray-darker: #222;
+$theme-black-light: #979797;
+$theme-black: #373737;
+$theme-black-dark: #272727;
+$theme-black-darker: #222;
 
 $theme-green-light: #adc;
 $theme-green: #019875;
@@ -127,8 +127,8 @@ body {
     @include gitlab-theme($theme-graphite-light, $theme-graphite, $theme-graphite-dark, $theme-graphite-darker);
   }
 
-  &.ui_gray {
-    @include gitlab-theme($theme-gray-light, $theme-gray, $theme-gray-dark, $theme-gray-darker);
+  &.ui_black {
+    @include gitlab-theme($theme-black-light, $theme-black, $theme-black-dark, $theme-black-darker);
   }
 
   &.ui_green {

app/assets/stylesheets/pages/profiles/preferences.scss

@@ -22,8 +22,8 @@
         background: $theme-graphite;
       }
 
-      &.ui_gray {
-        background: $theme-gray;
+      &.ui_black {
+        background: $theme-black;
       }
 
       &.ui_green {

lib/gitlab/themes.rb

@@ -15,7 +15,7 @@ module Gitlab
       Theme.new(1, 'Graphite', 'ui_graphite'),
       Theme.new(2, 'Charcoal', 'ui_charcoal'),
       Theme.new(3, 'Green',    'ui_green'),
-      Theme.new(4, 'Gray',     'ui_gray'),
+      Theme.new(4, 'Black',    'ui_black'),
       Theme.new(5, 'Violet',   'ui_violet'),
       Theme.new(6, 'Blue',     'ui_blue')
     ].freeze