Show color for values of type:list site settings with word 'colors' in t...

If a site setting is of type `list` and contains `colors` in its name, a bold line of the corresponding color will be displayed for every value in the list.

![image](https://cloud.githubusercontent.com/assets/282177/3869790/e4cc4b42-20a6-11e4-9a00-591d908ce9d4.png)

Discourse meta topic:
https://meta.discourse.org/t/improve-category-color-list-input-in-admin-panel/18455