Talking about red states versus blue states in a monolithic way is reductive and offensive. How this was done? The artist matched the percentage of blue in an RGB color picker to the percentage of the vote Barack Obama got and did the same for Romney and red. Green stayed at zero. So if a state had voted 100% for one or the other, you would see the bluest blue or reddest red your computer screen can produce. The reason all the colors are more or less in the middle is because no state went more than ~70% for one side or the other. Although if you zoom in you can see that DC is very bright with 91% for Obama.
