You can colour nicknames, you can even colour them differently depending on what status they have, if they are on ignore, etc.
Press
ALT+B and go to 'Colors'. Click on 'Add' and fill out the options you want. If you want all nicknames to be one colour, simply choose a colour and press 'OK'. If you want it to only apply in the nicklist, choose 'Listbox' from the drop down list. For it to only apply in the main channel window, choose 'Message'. Otherwise, choose the default option, which is both.
For further help, type
/help nick colors in mIRC.
If this is not what you wanted, and you want colour codes to be accepted into nicknames, see
this thread.
Regards,
