Leaves have color because of four kids of pigment chemicals in each leaf: Chlorophyll, Xanthophylls, Carotenoids, and Anthocyanins. In the spring and summer, sunlight triggers leaves to make lots of chlorophyll. That chemical helps plants make energy from sunlight (photosynthesis). Trees are very sensitive to environmental changes. As summer becomes fall and daylight shortens, less sunlight signals the leaf to prepare for winter. A leaf won't need energy, so it stops making chlorophyll. The green color fades and the reds, oranges, and yellows (that have always been there) become visible.