Are dogs really color blind?

In movies and television, whenever a dog's perspective is shown, the scene is often edited to black and white and gray—bright red roses look dull and dark, and freshly cut grass looks more artificial than natural. But is this common depiction of the dog-eye view true? Is man's best friend really blind to all colors?

Well, you might want to call Hollywood and complain, because movie producers get it wrong all the time. Dogs can't see black and white, but they are what we call "color blind," which means they only have two color receptors (called cones) in their eyes, whereas most people have three. Humans are considered color blind, and must have defective color vision, often the result of defects in the production of cone cells in the eye. Color blindness in humans may mean that one of the three color receptors in humans is not functioning properly, leaving some people with just two working cones. This type of color blindness is called dichromatism—different from the common human trichromacy—and is similar to dogs' color perception. So, technically, dogs are color blind (in the most human sense).

But if dogs are color blind, which colors can they see and which colors can't they see? Color receptors in the eye work by sensing only certain wavelengths of light. In humans, each cone perceives wavelengths of light that roughly correspond to red, green, and bluish-violet. By overlapping and blending the color spectrum perceived by the three human cones, we are able to see a wide variety of colors. However, in dogs, two color receptors in the eye sense wavelengths of light that correspond to blue and yellow, meaning dogs can only see a combination of blue and yellow. So instead of a bright red rose, the dog may see yellow-brown petals, and the vibrant green grass looks more dehydrated and dead.

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