Q: Why do the leaves change colors in the fall?
A: To keep it simple, the green we see on leaves is the chlorophyll (think solar panels) that convert the sun into food for the plant. Once the days begin to get shorter the plant or tree starts to prepare itself for winter. One of the steps to prepare itself is to stop producing the green chlorophyll.
This begins to expose other parts of the leaf which are often yellow and orange. Chemical reactions within the leaves can also create maroon and other red hues.