Biologists have shown that hummingbirds can distinguish between shades respectfully four colors, including the mixture of three monochromatic colors (UV, green and red). These results confirm that the vision of birds tetrachromatic. It probably helps the birds to communicate and to find food — about one third of flowers in plants and the plumage of the Hummingbird niespecjalnie. Article published in the journal Proceedings of the National Academy of Sciences.
The number of colours which distinguishes the animal, depends on the number of types of color receptors in the retina. In vertebrates, the role of color vision cones to play, most mammals, for example, there are only two types of such animals are called dichromats. The dichromats color space is one-dimensional, any perceived color can be reproduced by mixing two pure (monochromatic) colors. People with normal color perception are trichromats — we have three types of cones, they pick up red, green and blue colors, and the brain can perceive a mixture of colors and their shades.
The perception of a mixed color is due to the comparison of signals from cones of different types in the brain. For example, the color yellow seems to us, if it excites “red” and “green” cones. Yellow, red and green colors are called spectral — they are present in the rainbow and are either a single type of cones, or cones, of which the spectra are combined. Also consider the spectral hues between green and blue, but purple this definition is aspectually color, as forming its true colours — red and blue are at opposite ends of the visible spectrum.
Birds have a fourth type of cone sensitive to ultraviolet light, so these animals perceive more shades of colors and probably are tetrachromate. Color space of the four-dimensional tetrachromatic, any perceived shade lies inside of a quadrangular pyramid, in which each top — perceive one type of cones pure color. Spectral colors in birds are located along the three primary axes of color space, and respectfully colors they may be as many as five (trichromacy of them see only one Magenta).