Tetrachromacy is the ability to see color through four different “channels.” More specifically, an animal with tetrachromacy would have four different types of cone cells in each eye. A tetrachromate has a four dimensional color view, which just means that they see with four different primary colors as opposed to just three. It is thought that some fish, amphibians, reptiles, arachnids and insects are tetrachromates.
The best example of a tetrachromate is the bird, since most birds are tetrachromates. This means that birds distinguish a greater spectrum of colors than humans do. The zebra finch and columbidae are birds that rely on their tetrachromacy as integral parts of their lives. They use their vision to select a mate as well as find food. In a mate, they generally look for ultraviolet plumage.
Some researchers have hypothesized that some humans might be tetrachromates, and might just not realize it because they have no point of reference to compare their vision to. Women, in particular, are suspected of having this capability on a rare occasion because of their two X chromosomes. By having two X chromosomes, they could have extra cone cell pigments.