Unfortunately the boards are the colors they are. Some board makers are starting to come out with special editions with varying colors but generally speaking, you're at the mercy of the makers when it comes to board colors.
Edit: That said, it's worth noting that some boards, like my ASUS, have a thermal cover which covers a lot of the board up. I've seen people color that themselves, but that's not the exact same thing. Half the reason I grabbed the board for my build (in my signature) is because the thermal armor was a winter camo and I liked that far more than the usual red and black stuff.