This really isn’t a science experiment, but I thought I’d share the answer to this question my oldest daughter asked me recently.
According to this article from PupLife.com on How Dogs See Color, Dana K. Vaughan, Ph.D., Dept. of Biology, University of Wisconsin, Oshkos writes:
Many authorities have stated that “dogs are colorblind”, with the implication that dogs perceive only black, white, and shades of grey. In fact, this was not known for certain, but became “folklore”. Then, in the late 1980s, a definitive set of experiments was done at the University of California, Santa Barbara, by what may well be the world’s foremost research program on comparative color vision.
The key publication describing these experiments is: J. Neitz, T. Geist, and G.S. Jacobs (1989), “Color vision in the dog”, Visual Neuroscience Vol. 3, pages 119-125.
These experiments showed that dogs do see color, but in a more limited range than that seen by normal humans, who see the rainbow of colors described by “VIBGYOR”: Violet, Indigo, Blue, Green, Yellow, Orange, and Red (plus hundreds of variations on these shades). Instead, dogs see “VIBYYYR” (Violet, Indigo, Blue, Yellow, Yellow, Yellow, and Red). The colors Green, Yellow, and Orange all look alike to dogs; but look different from Red and different from the various Blues and Purples. Dogs are very good at telling different shades of VIB apart. Finally, Blue-Green looks White to dogs.
The simple explanation for these differences in color vision is this. The retinas of normal humans have three (3) types of color receptors, called “cones”. Each cone type is particularly sensitive to light of a narrow limit within the entire VIBGYOR range. That means that three different “cone lines” of communication run back to the visual part of the brain, which then compares the weight of the signals coming in from each of cone “line”. Different weights produce a perception of different colors. In dogs (and in “green-blind” humans), there are only two (2) types of cones, so there is less basis for comparison by the brain, and thus the perceived color range is more limited. In sum, dog color vision is “color-limited”, not “color-blind”.
So…there you have it. Dogs to see in color, just can not distinguish Green or Orange from Yellow and Blue-Green looks white to dogs.
Very interesting. And now we know.