Board Thread:Support Requests - Designing Your Wikia/@comment-27092850-20150811205237/@comment-24551580-20150811212624

Add the following code to Mediawiki.css:

li[data-user="userA"] .username { color: #CD0000 !important; font-weight: bold; font-style: bold; }

You can have multiple users with the same colouring like this (and of course, change the styling to whatever you want):

li[data-user="userB"] .username, li[data-user="userA"] .username { color: #CD0000 !important; font-weight: bold; font-style: bold; }

You may not be able to do it at the moment, because all the CSS pages may still be locked down, I haven't checked. You must also be an admin on that wiki, of course.