Bright red and purple colors are the result. The sugar maple, for example, is one of the most colorful fall trees. This is because the leaves are full of sugars that have been produced by the chlorophyll. The sugars react to the sunlight and to the cooler weather by turning bright colors. The Best and the Brightest.
All leaves change color before they fall from the tree.
But some leaves are more colorful than others. Just as some people's hair changes as they get older, some leaves can only change to yellow or green. Weather conditions are another factor that affects the color of fall leaves. The best and the brightest colors occur in years that have wet summers, cool fall nights, and warm sunny fall days. In Illinois, the best and the brightest fall trees are hard maples, red oaks, ash trees, sweet gum trees, and sassafras trees.