Total anthocyanin color is developed only in strongly acidic solutions. In isolation, anthocyanins have little color above pH 3.5, but in natural media, they become much more colored by copigmentation with other (plant) com- ponents, which may themselves be colorless. Based on observations of some relatively simple anthocyanins in vitro, the following scheme, related to pH changes, is generally accepted [17]: at a pH of approximately 3 or lower, the orange, red or purple flavylium cation predom- inates. As the pH is raised, kinetic and thermodynamic competition occurs between the hydration reaction on position 2 of the flavylium cation and the proton transfer reactions related to its acidic hydroxyl groups. While the first reaction gives colorless carbinol pseudo-bases, which can undergo ring opening to yellow retro-chalcones, the latter reactions give rise to more violet quinonoidal bases. Further deprotonation of the quinonoidal bases can take place at pH between 6 and 7 with the formation of more bluish resonance-stabilized quinonoid anions. At the pH values typical for fresh and processed fruits and vegetables, each anthocyanin will thus most probably be represented by a mixture of equilibrium forms.