Fall (autumn) is a time when many leaves are said to change colors. The truth is, though, leaves do not really change colors. Their true colors begin to show in the fall. The trees do not get the same amount of sunlight and the same temperatures in the fall and winter in order to produce enough chlorophyll to maintain their green leaves.
This book, Why Do Leaves Change Colors? gives a great explanation of the changing colors of leaves in the fall.
Click this link to listen and read along to the book: