As long as your nick list colors are turned on (in that Alt-B > Colors section that was already mentioned), you can also use this command (useful for a script):
/cnick * 10 @
That would set all users (*) to color 10 if they are an op (@).
/cnick Riamus2 4
That would set my nick to color 4 no matter what status I am.
For more information about it, type: /help /cnick