There is one.
Make sure this in in your headers:
<script src="/jquery.js"></script>
This goes in your footers:
<script type="text/javascript">
var memColor = new Array();
memColor[memColor.length] = ["MEMBERGROUP NAME","START HTML","END HTML"];
//Created by Agent Moose (revolutionx.smfforfree3.com)
if(location.href.match("topic,")){
for(f=0;f<memColor.length;f++){
$("div.smalltext").each(function(){
if(this.innerHTML.match(memColor[f][0] + "<br")){
$(this).prev().children().html(memColor[f][1] + $(this).prev().children().html() + memColor[f][2]);
};});};};
</script>
MEMBERGROUP NAME= the name of the membergroup.
START HTML= the begging HTML tag, ex: <font color='red'>
END HTML= the closing HTML tag, ex: </font>
To add more membergroups that change the username, add more of these lines:
memColor[memColor.length] = ["MEMBERGROUP NAME","START HTML","END HTML"];