Fixed issue with user calendar colors

## What does this MR do?

Fixes an issue with the colors added onto the user contrib calendar. The calendar was change recently to remove a library which affected how the colors where generated.

## What are the relevant issue numbers?

Closes #18505 

## Screenshots (if relevant)

![Screen_Shot_2016-06-13_at_09.33.10](/uploads/f17451d2eb805e9d75d859cd1691e0bc/Screen_Shot_2016-06-13_at_09.33.10.png)

See merge request !4614