Several species of animals are color blind or see muted colors, including dogs, cats, bulls and sharks. Many fish can see muted colors.
Other animals that are totally color blind, or monochromats, include dolphins and walruses.
Although it is hard to tell exactly what an animal sees, many mammals related to humans, such as chimpanzees and monkeys, can see colors as well as humans. Other mammals, such as dogs, can differentiate between a few colors, but their eyes are much weaker than a human's when it comes to differentiating between colors.
Scientists examine the eyes of different animals to be able to tell what colors they can see. They do this by studying the cones in the eye, which determine color sensitivity. The number, density and shape of the cones allow an animal to either see in vivid color, muted color or only in black and white. The cones are divided into three groups: red, green and blue. Those animals that are color blind lack cones. Behavior tests are also conducted on some animals to test for color blindness.
Until recently, dogs have always been thought to be color blind. Now, scientists know that most dogs can tell the difference between blue and yellow and can differentiate those colors from grey or white. They cannot, however, distinguish yellow from red or green.