Power Saver од Josh Volpe

"This theme changes the colors used by [Firefox] so the screen uses less power. Everything is just as view-able as normal. Power saver is ideal for anyone who uses a battery powered device or just wants to help the planet.

Power is saved by:
1. Using blacks and greys where whites and off-whites would normally be used.
2. Using darker tab colors with light text instead of visa versa.
3. Using primary colors instead of white, thus cutting the required screen power by over 60% in some cases.
4. Blues and Reds has been used instead of silvers and light greys, resulting in a cheaper electric bill and longer battery times." - Nate Watson

Enjoy!