It's a simple adaptation of the excellent Monokai color theme to IntelliJ IDEA, favoring "dark" choices, and optimized for Scala and Haskell.
The theme is also compatible with IntelliJ 12 (preview). It is particularly pleasent with the Darcula (Dark) theme:
In Mac OSX Lion, copy the .xml to:
~/Library/Preferences/IdeaIC11/colors/
In Windows, copy the same .xml file to:
%HOMEPATH%.IntelliJIdea11\config\colors
Don't forget to import the settings jar file with File -> Import Settings ...