Board Thread:Support Requests - Designing Your Wiki/@comment-4975807-20130825001614/@comment-25027816-20140820201854

Penguin-Pal wrote: You may find a few of the examples in this box helpful. Add the code that you want to your MediaWiki:Wikia.css. Replace Some user name with the user's username and follow the instructions in the comments (this need to be applied manually on each certain user). Also, if you import the custom chat JS and CSS pages, it's musch easier and doesn't require the body.ChatWindow prefix (also doesn't mix chat code with other wiki code).

You dont have to do the individual users thing if you dont wanna.