You do not need that plug-in to change the colour of your nick.
To use colour in your name, just open a conversation window, type /nick and a space and press ctrl-k. Then click the colour you want, type your name and press enter. If you want to use multiple colours, just use ctrl-k in your name multiple times, right before where you want the colour to show up. Take a look at the following example:
If you wish to use the plug-in, open a conversation window, type
/xcolornick and follow the instructions on the screen, or take a look at
NEW: ColorNick v2 !!! the ultimate nickname editor