Blue is a very rare pigment in nature. Creatures like blue butterflies or bluejays, are not actually made from blue pigments, rather they are produced by something called coherent scattering. This is a process whereby light waves get scattered to create the illusion of the colour blue. Blue skies and blue eyes are created this way. In his book Blue - In Search of Nature's Rarest Color, Kai Kupferschmidt explains, "when you see a blue flower – for instance, a cornflower – you see the cornflower as blue because it absorbs the red part of the spectrum. Or to put it another way, the flower appears blue because the color is the part of the spectrum that the blossom rejected." There are only a handful of animals that produce their own blue pigment. The blue mandarin fish (shown above) and the olive wing butterfly are two examples.