The human eye sees by light stimulating the retina that is made up of rods and cones. The cones help us perceive color during daylight conditions. These cones each contain a light-sensitive pigment that is sensitive over a range of wavelengths. If the gene coding instructions are wrong, then the wrong pigments will be produced, and the cones will be sensitive to different wavelengths of light. This results in a color deficiency. The colors that we see are completely dependent on the sensitivity ranges of the pigments.
While it is very rare to be totally color blind, there are many different types and degrees of colorblindness. More men than women are colorblind (one out of 12 men and one out of 200 women). The most common kinds of colorblindness involve weakness in the ability to perceive shades of red or green.