Colorblindness results from

It is a genetic condition caused by a difference in how one or more of the light-sensitive cells found in the retina of the eye respond to certain colors. These cells, called cones, sense wavelengths of light, and enable the retina to distinguish between colors.

Explanation:

Mutations in the OPN1LW, OPN1MW, and OPN1SW genes. The proteins produced from these genes play essential roles in color vision. They are found in the retina, which is the light-sensitive tissue at the back of the eye.