Colors matter, and Solarized is the slickest color scheme around. This style for the Colloquy IRC client includes both the light and dark variants, as well as some handy tricks like image embedding and optional backdrop images to distinguish public from private rooms.
Checkout the repo using git:
git clone https://github.com/eaton/solarized.git
Make sure Colloquy's styles directoy exists:
mkdir -p ~/Library/Application\ Support/Colloquy/Styles
Move the styles:
mv solarized/*.colloquyStyle ~/Library/Application\ Support/Colloquy/Styles/
You can now delete the git repository:
rm -r solarized
Start Colloquy and open the Preferences dialog:
Select new Style from Default Style drop down.