Dichromate (eye)
Dichromates (Greek di- , "double" and chroma , "color") are living beings that have two different types of cones (color receptors) in the retina .
While most vertebrates such as birds , fish , reptiles, and amphibians are tetrachromates , most mammals are dichromates (blue + green).
Humans generally have three types of cones for red, green and blue, making them trichromats . If one of these cone types fails due to hereditary reasons, those affected are called dichromates. Depending on which of the three cone types fails, this results in protanopia , deuteranopia or tritanopia .