‘Color blindness' or color deficiency affects over 3 million people in the UK in some form or another. Approximately 10% of males are color deficient but only 0.6-0.8% of females are color deficient. It is caused by a deficiency of certain chemicals in the retina of the eye.
Defective color vision can range from near-normal ability to distinguish colors, where typically the chemical for seeing red or green is slightly altered, to a high degree of confusion, where the chemical balance is considerably altered. In the most severe cases, deeper colors as well as pale colors will be confused, particularly if the lighting is poor.