I was curious so I did a little research into why leaves change color in the fall. The color change seems to be caused by the shorter days and cold temperature will speed up the change. Temperature and daylight affect a trees photosynthesis efficiency. Trees in turn stop producing green-tinted chlorophyll. Without this green tint leaves revert back to their yellow color. The leaves are actually always yellow, but you don't see it until the green fades away. This yellow pigment is from carotenoids, which is the same pigment that gives carrots their orange color.
The red color come from anthocyanins which are the same red pigments found in strawberries. Unlike carotenoids, anthocyanins only are produced in leaves during the fall. They are a protective mechanism for the leaves. They help leaves survive from fungus, drought, and excess UV damage. It's not fully understood why trees expend energy in the fall to produce these anthocyanins, but trees that turn red earlier than the other trees in that area is likely sick from a fungus or enduring other environmental stresses.