Well, like I said, you'd have to be a member of BOTH usergroups.
I.E., say a Staff Admin adds himself/herself to the moderator, super moderator, assistant admin AND supporter groups. That Staff Admin could then switch to any colored name he wants because he's a part of that group.
If you wanted to get two colored names, for example, you'd have to be a part of the supporter AND basic member groups to swap between the two.