Conjugated system Conjugated systems in pigments
 Conjugated systems have special properties that give their compounds strong colors. Many pigments have conjugated systems. For example, beta-carotene has a strong orange color. This comes from its long conjugated hydrocarbon chain. When an electron in beta-carotene's conjugated system absorbs a photon of light of the right wavelength, the electron can be promoted to a higher energy level. Often an HOMO to LUMO change is made by an electron if it is allowed by the selection rules for electromagnetic transitions.