I got bored the other week and created a WordPress styled theme for the Colloquy IRC client. It uses the standard WordPress colors and includes a nice WordPress logo in the background.
There are two variations of it– WordPress, and WordPress Busy. The only difference is that the latter hides events (join, part, nick, etc), which I find very useful for very busy rooms. Hence the name. 😉
To install download the zip file containing the styles and image, unzip and drag the variants folder into ~/Library/Application Support/Colloquy/Styles/
From there you should be able to activate the style in Colloquy from Style > Standard > WordPress / WordPress Busy