Most of us have heard that dogs are color blind. I looked into this and found that dog eyes have some differences than human eyes. One major difference is their minimum threshold for light is much lower than ours. The central 25% of the retina consists of mostly rods (ours is mostly cones). This explains why dogs are better at detecting moving objects than stationary ones. Contrary to popular belief, dogs do have some color vision. Humans have three types of cones. Dogs only have 2, so they do not experience the same spectrum of color that we do. It is understood that blues and yellows are seen the best.
For more information: http://www.northwestanimaleye.com/what-animals-see.pml