[5][6][7] The OPN1SW gene provides instructions for making a protein that is essential for normal color vision.

This protein is found in the retina, which is the light-sensitive tissue at the back of the eye.

[8] In response to light, the photopigment triggers a series of chemical reactions within an S cone.

These reactions ultimately alter the cell's electrical charge, generating a signal that is transmitted to the brain.

The brain combines input from all three types of cones to produce normal color vision.