Two Questions
 

How do i chat in jj2 with other players in game?
How do I color my name?

To chat in-game, press t, type your message, and press enter to send.
To color your name, beat the game 50 times and you will get the choice of green colored text. Another 50 times gets you red, and so on.
Actually I'm lying about the colors. The chatting part works, though.

For colors you can use one of the many player info editing programs, like Jed, or just use regedit.

Or use gry's 1.23+ patch which will allow you to use pipes or any other character when naming.

Thanks you all