Type this in as your signature in your profile or anywhere for that matter.
Your Name Here </B>
B for bold, I for italic and use the US spelling 'color'.
The numbers are in hexidecimal. First pair for red then green then blue, 00 for no colour, FF for max colour. eg 000000 is black and FFFFFF for white. Just experiment, there is lots you can do with simple HTML.
I keep my code simple and short. Overdoing it will clutter up the post for people recieving it by email.