Distant objects appear more blue because of another optical effect called aerial perspective.īlue has been an important colour in art and decoration since ancient times. An optical effect called the Tyndall effect explains blue eyes.
The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. Most blues contain a slight mixture of other colours azure contains some green, while ultramarine contains some violet. The term blue generally describes colors perceived by humans observing light with a dominant wavelength between approximately 450 and 495 nanometres. It lies between violet and cyan on the spectrum of visible light. Clockwise, from top left: A Ukrainian Police officer on duty Tiles of the Sheikh Lotfollah Mosque, Iran Red-legged honeycreeper Copper(II) sulfate Sea at the Marshall Islands Planet Earth.īlue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model.
