Stories by W. A. H. Rushton

Color Vision depends on three types of cone cell, each containing one of three visual pigments. Those who are color-blind either lack one of the pigments or have an anomalous pigment in one type of cone

One pigment records images in black and white when the light level other pigments distinguish is raised. The blue-sensitive is low; two the level between green and pigment is yet to red when be found