You can test the color blind of your children by detecting their symptoms when they see some colored objects. Most of children are either "red weak" or "green weak", which means that they are unable to distinguish these kinds of colors or colors that contain these hues. So if you find your children often mix up red color and green color or they have trouble distinguishing different colors, they may have color blindness. You'd better take them to see a doctor as soon as possible.
According to Dr. Claire McCarthy, color blindness affects one percent of females and eight percent of males. To know if your children is color blind, just visit the website ColorVisionTesting.com where can give your child a color blindness test. At that site,there is a few seconds to distinguish numbers and shapes within dot patterns in cards. And that cards are helpful to let you know if your kid has protanomaly.