Green on a background of white and grey backgrounds worked. It was also effective when set on a background of red or blue.

The participants performed tests of creativity after observing a colored graphic on a screen. After completing their tasks they reported on their mood and how they felt they did on the test. People who saw green graphics before evaluation ranked themselves higher than those that didn’t.

Citation: Stephanie Lichtenfeld, Andrew J. Elliot, Markus A. Maier and Reinhard Pekrun “Fertile Green: Green Facilitates Creative Performance” Personality and Social Psychology Bulletin 38(6) 784–797 (2012)