Okay, so I was able to create some groups: like Honourary Members.
But, that legend appears under peoples username only in posts. And, I would like for it to appear on the front page also, next to Administrator and Moderator, and that when you see who's online, you can also see who's who. They're colored.

Is that possible???

Yes you can, make sure the group you made is closed by going to admin panel=>Users & Groups=>Groups=>Group Administration. Now click on this icon next to the group you ant to modify and search for this option "Group status:" set to "Closed group".

Okay, I did that now...but
It still doesn't show up on the front page, where the legends are, for Administrator and Moderator o.O

have you given it a colour and ticked to colour group members>

also go to admin>>>users and groups>>>user settings to make sure you have set yes to colourised user names enabled.

Hmm..Okay, now it worI tried to click enable that option, but it just didn't work for some reason. o.O

then even we the admins lost the colors.

well, now it's okay, so thanx!!!