Question: Why do leaves change color in the fall?

Paige Brown answered on 22 Jun 2012:

I love this question! Leaves change their color in the fall because of the different pigments in the leaves that absorb sunlight. Normally, leaves have high contents of the chlorophyll pigment that absorbs almost all light except green light. Plants use these pigments to absorb a large spectrum of light from the sun, using the sunlight to create sugars in a process called photosynthesis.

In the fall, as trees start to ‘shut down’ photosynthesis and prepare to live off all the sugars they made over the summer during the winter months, the traditional chlorophyll pigments are depleted/degraded. What are left are some of the other pigments that leaves typically contain other than the familiar chlorophylls, that absorb light in other regions of the light spectrum, making the leaves appear different hues of yellow, red, orange. When all the pigments are gone and the leaves begin to die, they turn brown. Some of the chemicals that make leaves vibrantly red in the fall, for example, are derived from sugars (which makes sense, because leaves spend all summer long making sugars, so in the fall as the green pigments leave and sugar accumulates, the leaves may appear red!) Reference: http://en.wikipedia.org/wiki/Anthocyanin

From About.com:

YELLOW (caused by the chemical xanthophyl)
Ash, basswood, birch, beech, butternut, elm, hickory, mountain ash, poplar, redbud, serviceberry, willow and some maples (boxelder, mountain, silver, striped and sugar).

RED (caused by the chemical anthocyanin)
Some oaks, some maples, sumac and tupelos.

ORANGE (caused by the chemical carotene)
Some oaks and maples.

RED OR YELLOW
Sugar maple, dogwood, sweet gum, black gum and sourwood.