How can I make the thead gradient different for my premium usergroup?

[Luggruff]

Lets say that you have a tablecell that says:

<td class="thead">&nbsp;</td>

..where the gradient for the thead class is BLUE, and you want it to be RED for the ADMIN usergroup, the you just make an own css class for the RED one called something like "theadAdmin" with the same settings as the original thead class and write this instead:

<if condition="is_member_of($bbuserinfo,6,)">
<td class="theadAdmin">&nbsp;</td>
<else />
<td class="thead">&nbsp;</td>
</if>

only, I don't know how to put more than two conditionals like this into it for more usergroups.
But if you only have one usergroup you would want to change this for, then it works.