Probably one of the most frequently asked questions about dog's vision is whether dogs see colors. The simple answer-namely that dogs are colorblind-has been misinterpreted by people as meaning that dogs see no color, but only shades of gray. This is wrong. Dogs do see colors, but the colors that they see are neither as rich nor as many as those seen by humans.
The eyes of both people and dogs contain special light catching cells called cones that respond to color. Dogs have fewer cones than humans which suggests that their color vision won't be as rich or intense as ours. However, the trick to seeing color is not just having cones, but having several different types of cones, each tuned to different wavelengths of light. Human beings have three different kinds of cones and the combined activity of these gives humans their full range of color vision.
The most common types of human colorblindness come about because the person is missing one of the three kinds of cones. With only two cones, the individual can still see colors, but many fewer than someone with normal color vision. This is the situation with dogs who also have only two kinds of cones.
One amusing or odd fact is that the most popular colors for dog toys today are red or safety orange (the bright orange red on traffic cones or safety vests). However red is difficult for dogs to see. It may appear as a very dark brownish gray or perhaps even a black. This means that that bright red dog toy that is so visible to you may often be difficult for your dog to see. That means that when your own pet version of Lassie runs right past the toy that you tossed she may not be stubborn or stupid. It may be your fault for choosing a toy with a color that is hard to discriminate from the green grass of your lawn.
Take a look at the two photo's below, the photo on top is how we see things, the photo on the bottom is through the eyes of a dog.