A flat dark color scheme based off the base16-tomorrow dark color palette. It's not the prettiest, but I think it's easier on the eyes than the bright white of standard Redmine.
Only tested with Redmine 2.5-stable.
As always, THANKS to Chris Kempson for the base16 color palettes!
1.0 - Created.
1.0.1 - Updated background color on html for short pages.
1.0.2 - Added flash notice color.
1.0.3 - Added code for pre.
1.1 - Fixed issue with previews and tags plugin I use.