Where on the profiles or on the forums?

If on the forums, it's pretty simple, just wait for the situation to come around and start one. Then put it's name in your signature and beside it put: PM midnight ride to join.
To make it coloured text you go: [.color=greenreadwhatever]*blah blah bla*[./color]

make sure you take away the dots at the start of the brackets, or else it won't work.

In the profiles it's simple, just go to your profile page through the link in the top right corner of the screen. Once there, go to the columns of options and it says:

User Menu | Bands | Groups | <-- click groups.

Scroll down to a button that says create new group. From there, it's easy as piece, but, I don't think you can have coloured text on your group profile, you can always try though. Just use the tags again.