Textual-Monokai is a Textual IRC style for OSX. You can find Textual at http://www.codeux.com/textual/ or on the App Store.
It was a mix of Simplified Dark theme bundled with Textual and the Solarized color scheme and then added Sublime Text 2's Monokai theme to it.
Checkout this git repo into ~/Library/Application Support/Textual/Styles in a sub-folder and it will be an available option in the Textual preferences pane.
cd ~/Library/Containers/com.codeux.irc.textual/Data/Library/Application\ Support/Textual\ IRC/Styles/
git clone https://github.com/bettin/textual-monokai.git