If people can't tell all kinds of colors, we can say they are color-blind. Most color-blind people can see 1 but cannot tell red from green. Very few people are blind to all kinds of colors, but they may see black and white. It's 2that many color-blind people don't think they are color-blind. Well, the reason is that they don't know that they can't see or name the real colors. This can be dangerous when a color-blind person is passing the 3Some people are 4color-blind. And though doctors have tested many times on the reason for color-blindness, there is still no good reason for it at all. So there is still no way to 5the color-blindness.