How can I achieve this?

[arcaneex]

http://img17.imageshack.us/img17/9773/814b87e03ec640b79353146.png
I want the color to change based on the user rank, and to change font to something else.

 

[Jake Bunce]

You mean the big Administrator title? You can use HTML group titles with inline CSS:

http://xenforo.com/community/threads/is-there-a-way-of-colourising-the-user-title.12727/#post-167567