Everytime I hear 'Black', I think of the painter sketches from The Fast Show. Its other association is either premium (Black card etc) or death (in the Europe and USA).

So how can black be a force for good - how about saving a tiny amount of screen energy:

http://www.blackle.com/

Just imagine if for every Google search it used black as a background how much energy could be saved without a loss in user experience. What a cool idea!