The authors here propose that humans prefer colors like blues and greens because those colors and ecologically healthy (blue skies, clean water, healthy vegetation), and do not prefer colors like brown because it's associated with stuff that is ecologically unhealthy (like crap and things that are rotting).
Then they went about testing the theory by correlating color preference with objects that were judged favorable or unfavorable by the test subjects. Although the ecological theory incorporates parts of several other color theories, the data seems to support this idea more than previous theories. Link
http://blog.xkcd.com/2010/05/03/color-survey-results/