This has been mentioned before, but by simply using colored circles for their controller buttons, they are ignoring the needs of a lot of color blind gamers. This is why every console manufacturer has symbols on the buttons. Color coding doesn't work so well when a significant percentage of your players can't differentiate between green and red.

This could be solved very easily by picking some symbols to go along with the colors. Of course, our patent and trademark laws are ridiculous and it's highly likely that Microsoft has already patented the letters X, Y, A, and B...