Colorblindness is a illness that patient could not sense either red and green, or blue and yellow. For the patients suffer from red and green colorblindness, they would sense the lower frequency light (red, orange, and yellow) as yellow color, and see the higher frequency light (green, aquas, blue, and purple) as blue color. As for the yellow and blue colorblindness, the lower frequency light would shift to red, and higher frequency light would shift to green.