Many people believe that dogs and cats are completely color blind and can only see in shades of black and white. In fact, scientists believed this, too, for many years. But how could they know? It's not like you can give a dog or a cat a vision test and ask them to tell you what colors they see, right?
Scientists actually use sophisticated tests involving food and colored panels to test whether animals can sense different colors. For example, if a dog could tell the difference between colors enough to choose a light-colored panel, it would receive a treat.
These tests showed scientists that dogs and cats can indeed see colors — just not all the same colors that humans can see. Scientists now believe that dogs and cats can see blue and green.
This means that a dog, for example, could tell the difference between blue and yellow but not red and green. So, if you see a dog run a red light, it's not his fault! He might have thought it was green!
Like dogs and cats, humans can also have color blindness — also called color vision deficiency. This doesn't necessarily mean that color blind people only see things in black and white. It usually means that they can't see certain colors and therefore have a hard time telling the difference between those colors.
Being color blind can make it difficult to match your clothes, but it's rarely a serious problem. Most color blind people can do everything they want to do. Sometimes they just have to come up with special adaptations. For example, people who can't tell the difference between red and green can still drive, because they know that the red light is usually on the top and the green light is usually on the bottom.
Color blindness is caused by problems with the cones in your eyes. Cones are special cells on your retina that sense color. People with normal color vision have three types of cones: red, blue and green. Cones send information to your brain, which decodes it so you “see" those colors and combinations of them for full-color sight.
When these cones don't work right, your brain doesn't get the proper messages from your eyes. The result is that you can't see certain colors and can't tell certain colors apart. For example, a blade of green grass might look gray. This is what doctors call color blindness.
Color blindness is nearly always an inherited trait that's passed down through genes from your parents. Boys tend to be more likely to be color blind than girls. In fact, one in 12 boys is likely to have some form of color blindness. If the cones in the eyes are damaged through physical contact or chemical exposure, color blindness can also occur.