[Nibbles]

Where would you get the biggest return?
Putting energy into telling people shut off your monitors and computer, or telling people to make black websites? I will make this easy: The former.
Also, there is such a small difference between black and white that the side effects of the color is more influencing - people very well could use more electricity during the day when they are surrounded by a black screen (they might want to turn on a light if the colors don't look good, for example).

We don't even know if CO2 is the chief cause at all (CO2 emissions is where all the political money goes because it is the only thing we know how to fix, not because it is correct). It is incredibly difficult to factor in the effects of cloud cover, energy efficiency, energy conversion (greenhouse gases), solar activity, snow/ice cover, and sea levels into a single model. (One model suggested that a tree generates more heat in the process of photosynthesis then the carbon dioxide it removed from the air...)

Anyways, this isn't the best place to focus your work if you are looking to make a difference.