Student Research - Leaves and Colors
Leaf colors come from "pigments." The green color in leaves comes from the pigment chlorophyll. Other pigments make leaves orange, yellow, red and a purplish color.
Leaves always have orange and yellow pigments in them, but we can’t see these colors until the fall when leaves stop making green chlorophyll. When leaves do make green chlorophyll we can’t see the other colors.
As winter approaches leaves might turn red or purplish. The pigments that make these colors only appear in the fall because they need cool nights to develop.
Chlorophyll makes this leaf green. Leaves must have chlorophyll to do photosynthesis. This leaf will use light from the sun and the carbon dioxide it breathes in to do photosynthesis.
Why do leaves change color?
As we get closer to winter, days get shorter and nights get longer. When this starts to happen leaves get the message that winter is coming and stop making chlorophyll. Why? Because when winter comes they will not have the sunshine they need to do photosynthesis so they will not need chlorophyll. Without chlorophyll leaves are not green.
Nature does not want to waste energy making chlorophyll when it will not need it. So, it stops making it until springtime 
to protect the tree from using precious resources.
This is a photo of bigtooth maples at Lost Maples State Natural Area:
Want to visit Lost Maples? Check their website before going for a report of how the leaves look. http://tpwd.texas.gov/spdest/findadest/parks/lost_maples/foliage.phtml
Why do some leaves change color in the fall?
Leaf colors will depend on three things:
- How much chlorophyll they have in them
- How much sugar they have in them
- The weather
The more chlorophyll leaves have the greener they will be.
The amount of sugar and sunlight leaves get in the autumn determine the colors they become. The more sugar and sunlight the more red you will see in the leaves.
Some leaves don't change colors. They just become dry and shrivel up.
The weather throughout the year will also affect the colors of the autumn leaves.
Check out this 5-minute video about how and why leaves change colors:
http://pbskids.org/dragonflytv/show/leaves.html