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.
Jay Neitz at the University of California, Santa Barbara, tested the color vision of dogs. For many test trials, dogs were shown three light panels in a row--two of the panels were the same color, while the third was different. The dogs' task was to find the one that was different and to press that panel. If the dog was correct, he was rewarded with a treat that the computer delivered to the cup below that panel.
Neitz confirmed that dogs actually do see color, but many fewer colors than normal humans do. Instead of seeing the rainbow as violet, blue, blue-green, green, yellow, orange and red, dogs would see it as dark blue, light blue, gray, light yellow, darker yellow (sort of brown), and very dark gray. In other words, dogs see the colors of the world as basically yellow, blue and gray. They see the colors green, yellow and orange as yellowish, and they see violet and blue as blue. Blue-green is seen as a gray. You can see what the spectrum looks like to people and dogs below.
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.