Three types of pigments are involved in autumn color.

• Green is produced by chlorophyll, which is necessary for photosynthesis — the chemical reaction that turns sunlight into plant sugars. Trees in the temperate zones store these sugars for their winter dormant period.
• Yellow, orange and brown are made by carotenoids — seen in corn, carrots, daffodils, rutabagas, buttercups, and bananas.
• Red and purple come from anthocyanins. These water-soluble pigments appear in the watery liquid of leaf cells, and give color to cranberries, red apples, concord grapes, blueberries, cherries, strawberries, and plums.

Both chlorophyll and carotenoids are present in leaf cells throughout the growing season. Most anthocyanins are produced in the autumn, in response to bright light and excess plant sugars within leaf cells.

During the growing season, leaves appear green because chlorophyll is continually being produced and broken down. As night lengthens in the autumn, chlorophyll production slows down and then stops. Eventually, all the chlorophyll is destroyed, which allows the carotenoids and anthocyanins in the leaf to show their colors.

Certain colors are characteristic of particular species. Oaks turn red, brown, or russet; hickories, golden bronze; aspen and yellow-poplar, golden yellow; dogwood, purplish red; beech, light tan; and sourwood and black tupelo, crimson. Maples differ species by species — red maple turns brilliant scarlet; sugar maple, orange-red; and black maple, glowing yellow. Striped maple becomes almost colorless. Leaves of some species simply shrivel up and fall, exhibiting little color other than drab brown.

The timing of the color change also varies by species. Sourwood in southern forests can become vividly colorful in late summer while all other species are still vigorously green. Oaks put on their colors long after other species have already shed their leaves. These differences in timing among species seem to be genetically inherited, for a particular species at the same latitude will show the same coloration in the cool temperatures of high mountain elevations at about the same time as it does in warmer lowlands.