[WetWired]

Myself, I've never written anything like that, but what you need to do is put something like <span class="rainbow"></span> as the markup for the usergroup, then have javascript that runs at the end that does a document.getElementsByTagName("span") to get all the spans, then itterate through them. For each one with className="rainbow", you'd retrieve the innerHTML, break it into letters, add the color markup, and write it back.

Again, I'm a novice when it comes to JS, especially the string stuff you'd need to use; if what I've given you isn't enough, you'll need to find other help.