They lead the way, and others soon begin following. Yet why is it that some trees are so colorful, and others simply turn brown. Changing Colors Indian legend says that leaves change from green to red in the fall when celestial hunters slay the Great Bear. Other leaves are turned yellow by fat splattering out of the kettle as the meat is cooked. There is another, somewhat more scientific reason.
Most leaves are green during the growing season.
There are some plants such as purple leaf plum, some Japanese red maples and barberries, which have colorful foliage all season, but most plants have chlorophyll hiding their other colors. The chlorophyll gives leaves their green color and is what is within the cells that manufacture food, through a process called photosynthesis. As fall approaches, the days get shorter, and the nights get cooler. This starts the shift toward dormancy. When the trees start slowing down in growth, they can't use the food that is produced by the leaves.