Sky blue refers to a collection of shades comparable to that of a clear daytime sky. Typically it is a shade of cyan or light teal, though some iterations are closer to light azure or light blue. The term is attested from 1681. A 1585 translation of Nicolas de Nicolay's 1576 Les navigations, peregrinations et voyages faicts en la Turquie includes "the tulbant [turban] of the merchant must be skie coloured".

Cyan is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue.

The sky is an unobstructed view upward from the surface of the Earth. It includes the atmosphere and outer space. It may also be considered a place between the ground and outer space, thus distinct from outer space.