[Kirk Y]

Create a plugin at hook location "postbit_display_start" with the following:

switch ($this->post['usergroupid']){
    case 6:
        $color = "green";
        break;
    case 2:
        $color = "red";
        break;    
}

Change the Number in each Case statement to the Usergroup ID that you're assigning that particular color to.

Find in your respective postbit template:

<if condition="$post['usertitle']"><div class="smallfont">$post[usertitle]</div></if>

Replace with:

<if condition="$post['usertitle']"><div class="smallfont"<if condition="$color"> style="color:$color"</if>>$post[usertitle]</div></if>