http://www.puplife.com/dogcaretips/h...seecolors.html
This link explains how motion has a lot to do with how they see, cool!
Actually, the most acceptable hypothesis is that the dogs are able to see only some colors, like blue and yellow. The rest of the colors would be detected as gray variations."
Here is from another site. I once saw a picture in a book- 2 actually. One normal and one in the colors dogs are supposed to see either only blues and green or only reds, oranges and yellows, I don't remember.