Heres a short tutorial on how you can create your own customizable usergroup legend on your forum index.
1) Go to Admin CP > Templates & Style > Templates > (your default template) > Index Page Templates > index_boardstats and find:
Code:
{$whosonline}
Add this below it:
Code:
<tr><td class="tcat"><span class="smalltext"><strong>User groups</strong></span></td></tr>
<tr>
<td class="trow1"><span class="smalltext">
TEXT HERE
</span>
</td>
</tr>
2) Go to Users & Groups > Groups > (Choose a group) >>Username Style, copy everything
3) Go back to Admin CP > Templates & Style > Templates > (your default template) > Index Page Templates > index_boardstats
and replace "TEXT HERE" with your copied Username Style
replace ?{username} with the name of the user group.
4) Repeat with any other usergroups you want to add to the usergroup legend, add a comma and space (, ) after each one.