What kind of person is a color-blind person? He can’t ______ all kinds of colors

If people can’t tell all kinds of colors, we can say they are color-blind.(12)Most color-blind people can see yellow and blue, but cannot tell red from green.(14)Very few people are blind to all kinds of colors,(13)but they may see black and white. It’s interesting that many color-blind people don’t think they are color-blind.(15)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 traffic lights. Some people are born color-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 cure the color-blindness.
Questions 11 to 15 are based on the passage you’ve just heard.
11.What kind of person is a color-blind person?
12. What kinds of colors can most color-blind people see?
13. For those who are almost blind to all colors, what kinds of colors can they only see?
14. How many people are almost blind to all colors?
15. Why is it dangerous for a color-blind person to pass the traffic lights?