The color of carotenoid pigments is the result of the presence of a system of
conjugated double bonds. A minimum of seven conjugated double bonds is required for the
yellow color to appear. The increase of double bonds results in a shift of the major adsorption
bands to the longer wavelengths, and the hue of carotenoids becomes more red. Because of
the highly conjugated double-bond system, carotenoids show ultraviolet and visible
absorption spectrum characteristics. For most carotenoids, three peaks, or two peaks and a
shoulder, are absorbed in the range of 400–500 nm.