Mesozoic
Although mammals originated in the Upper Triassic, they did not live like dinosaurs. Mammals spent most of the long Jurassic and Cretaceous periods as small nocturnal animals living mainly in forests. Most lost their color vision. Mammals today have some color vision. Most have red-green color blindness, with only two types of cone cells. Some primates evolved a third type of cone cell, which gives them trichromacy. Color is needed in forests to spot ripe fruit.