My son was tested when he was 2. He was asked to trace the picture on the chart. We could tell right away that he was color blind. We have redone the test twice and the results are always the same. If you want to do a quick screening yourself just show the child some neon colors and then have him match them to some basic colors. Like show him neon pick and he will probably match that with a regular pink. Peach looks like green.