Board Thread:Support Requests - Getting Technical/@comment-16553729-20160606150449/@comment-1757994-20160606200358

It would be possible to do it with JavaScript, although it would mean extra queries for every page.

Basically, after the page loads initially, look for any  tags with an href pointing to a User: page or Special:Contributions or similar. Make a list of all users, then query their group membership. Based on their groups, add custom classes to the  tags to change their colors. The classes would be defined in MediaWiki:Common.css.

An annoying complication would be that Wikia article/blog comments are loaded after the initial page load, so coloring usernames in comments would require more work. At the moment, I'm not sure how much more.