Copy the xml file or clone this repository into your RubyMine preferences directory. It's super-easy! Then edit and customize as you'd like.
Select the scheme at IDE Settings | Editor | Colors & Fonts. If you expand the Colors & Fonts group you can choose background colors and styles for the many supported languages and styles.
For more schemes, check the 'old' official list. at http://devnet.jetbrains.net/docs/DOC-1154
Copy the xml file here:
or do a
git clone git://github.com/oma/RubyMine-Scheme.git .
in the colors directory (create it if it doesn't exist). If you have a different RubyMine version, use that one.