tetrachromacy

tethracromacy  is an ability to see much greater color depth than the ordinary person.

An ordinary person can perceive a million different hues of colors. The power to distinguish the hues comes from cells in our eyes called cones. In the average person, there are three types of cones each of which is triggered by different wavelengths of light.

The most people have three types of cones, and are said to be "trichromats." Color blind individuals have only two types of cones and they are said to be "dichromats." Almost all animals, including dogs and New World Monkeys are dichromats

However, scientists have long believed that there are people with four cones who can see a wider range of colors than most of us can detect. These persons are called "tetrachromats," and can see a hundred million colors. From the perspective of such people, the hues familiar to trichromats fracture further into more subtle shades of differences that have not been given names since most of us are trichromats who cannot see these shades and name them.

men who possess two normal cones and a mutant cone that is less sensitive to either green or red. This makes it difficult for such people to distinguish the two colors. De Vries incidentally tested the daughters of one of the color blind men and found that they could detect a wider range of hues of red than average persons. He found that while the color blind men had two normal cones and one mutant cone, the mothers and daughters of the color blind men had a mutant cone and three normal cones, that is, a total of four cones. He believed that the extra cone explained whey the women seemed able to distinguish a wider variety of hues of red. But De Vries did not have the opportunity to investigate the phenomenon further.