In fall most leaves, except for the needles on a evergreen, change color and eventually fall off. The reason evergreens don't loose their needles is because they are covered in a waxy coating, but all other trees decided to do things other ways. They decided to lose their leaves every year, then get them again in the spring. They reason leaves change colors and the way trees loose their leaves kind of go together. In the spring and summer the leaves are green because of this chemical it the leaf called chlorophyll. Then at the start of fall, the leaves usally turn yellow, red or orange. The leaves turn different colors from the different chemicals in the leaves. The leaves that turn yellow or orange turn those colors from the same chemicals called carotene and xanthophyll. Most of the year the leaves are green because those two chemicals are overthrown by chlorphyl, so they can't come out until it starts to wear away in the fall, though they are in the leaf year round. Some leaves turn the color red because of a chemical called anthocyanins which is not in the leaf year long. It only comes out when the chlorophyll starts to break down. Finally, towards the end of fall, the leaves start to turn brown. They turn the muddy color because there isn't much more chemicals in the leaf, and it is just the unwanted stuff of it all. Last the leaf can't get anything from the tree anymore, so it just breaks away, leaving a scar where the leaf was.