By Dr Ivan R. Schwab
Dogs see colors, but their span of color vision closely resembles the array of colors seen by “color blind” males.
About 8%, or 1 out of 12 males (humans) and about 1 out of 200 females are “color blind.” We use that term to describe individuals who are color deficient, but they are not truly color blind. The eye has cells that perceive color and these are called cone photoreceptors or “cones.” We use another set of photoreceptors called “rods” for the black and white vision of dim light or nighttime. Our cones contain three visual pigments each of which responds to a different spectrum of wavelengths of light. It is these three visual pigments that combine their signals to permit us to have color vision by blending the signals, depending on the wavelengths received. Although it is an over-simplification, and misleading to some extent, we can describe our visual pigments as blue, green, and red. The brain receives the input from these three channels and then interprets the color we see. At least two different color channels are needed for color vision because the brain needs to “compare” these two different channels to determine color.
So, almost all color blindness in humans is not true color blindness but would be better described as color deficiency.
Now, let’s go back to your dog. Normal dogs have two different visual pigments in their cones, and much like humans afflicted with so-called “color blindness.” But they would see color. The color input would be weaker to some extent because dogs have fewer cones than we do because they are evolutionarily closer to their nocturnal ancestors. Cones are needed less, if at all, at night.
So, what about the other pets in the household? Your cat will have a similar color distribution as your dog although there are some subtle differences.
Hence, the answer to the question of “Does my dog see in color?” is “yes” although not as well as you probably do.
Dr. Ivan R. Schwab, a professor at the University of California, Davis, is the author of Evolution’s Witness: How Eyes Evolved. He also has a blog which you can find here.