Chemical changes that turn leaves from pale green in spring to dark green in summer to yellows and reds in fall are quite complex. The green pigment in chlorophyll, and stored in plastids, diminishes and is replaced by a pigment color without chlorophyll. The exact color is determined by each tree species.
There are three major components for pigment change in leaves. Plastids (1) are minute leaf structures that carry green chlorophyll and color the summer forest. Carotenoids (2), stored in plastids, and anthocyanins (3) in leaf sap are the leaf paints (pigments) that color the forest of autumn.