Why do leaves change color?
Less sunlight and cool (but not necessarily freezing) fall temperatures result in less production by leaves of green pigment (chlorophyll). Consequently, other leaf pigments like yellow (xanthopyll), orange (carotene) and red (anthocyanin) become more prominent. The intensity of the color in a leaf depends on the amount of sugar stored in the leaf and the amount of autumn sunlight it gets. Brown pigment (tannin) remains after all the other pigments have disappeared.
