Dogs do see in color, but their perception of color is not the same as it is for people. They cannot distinguish between red, orange, yellow or green. They can see various shades of blue and can differentiate between closely related shades of gray that are not distinguishable to people.

When comparing dog and human vision, people are better at depth perception, color perception and seeing minute details of an object. Dogs are better at seeing in dim light, responding to an image rapidly and detecting the slightest motion. They also have better peripheral vision.

In a 1995 study published in the Journal of the American Veterinary Medical Association, researchers dissected canine retinas and found many color-sensitive cones that indicated that there was at least an anatomical potential for color vision in dogs. The researchers also used behavioral discrimination testing and electrical photo tests to determine the light wavelengths that stimulated these cones. The dogs in the study could not differentiate between middle-to-long wavelengths of light, which to people appear as green, yellow, orange or red.

Dogs are able to differentiate between various shades of blue and violet, shades that people cannot tell apart. It is theorized that people have a yellow pigment in the lens of their eye that blocks short wavelengths (blue) light and significantly reduces sensitivity to violet and blue light. Dogs do not have this yellow pigment and therefore can see very subtle color changes.

If you are feeling curious, you can try testing your own dog to see if he can tell one shade of color from another. First, try to teach your dog that a blue towel always elicits a positive response. Then put out a green, a red and a blue towel and see if they pick the right color. This is a very crude test but it may work.