Giving other group admin abilities

I know this is a 'nooby' question but I've forgotten how to give admin abilities to other groups.
Enlighten me someone.

Just add them to the Admin group.

But I want that group to have their group color show, not the admins group color.

Well add them to another hidden group, put them into that group as well.
Then give this group a higher rank, so the color will be of this group but he will also be a admin.

See if it works.