This is the most common color of autumn leaves; about 70 % of shrubs and trees at the Harvard Forest produce anthocyanins during the senescence of the leaves. In these leaves, the actual shades of red are the consequences of the amounts of anthocyanin, the retention of carotenoids (or even a little chlorophyll).
http://harvardforest.fas.harvard.edu/leaves/process
Climate change, then, could have a lasting effect on fall foliage, as the cycle of drought and deluge changes, and temperatures warm overall. A longer growing season can keep trees more green later into the fall, when a shock of frost can make them drop leaves before they complete the color-change process.
http://www.goodhousekeeping.com/home/a18922/why-do-leaves-change-color-0909/
When photosynthesis shuts down, the chlorophyll in leaves that makes them appear green breaks down. What colors come next depend on the following: Relatively warm sunny days promote the creation of sugar within the leaves.
http://www.cnn.com/2012/09/19/travel/why-leaves-change-color/index.html
Why do some leaves burst into various shades of red while others turn orange or brown -- or some combination of all three? Ed Sharron, a science communication specialist with the National Park Service's Northeast Temperate Network in Vermont, explains the science behind the beautiful colors of fall.
http://www.cnn.com/2012/09/19/travel/why-leaves-change-color/index.html
That's a very exciting question -- with an equally exciting answer! Inside a leaf there are millions of little packages of color in green, yellow and orange. 1  The green packages are called chlorophyll. 2  The yellow packages are called xanthophyll. 3  The orange packages are called carotene.
http://www.kidzone.ws/plants/autumn1.htm
Such leaves are a pale green in color, or perhaps yellow-green from the mixture of chlorophyll and carotenoids. Most interesting are leaves that turn red, because this color is the result of the active synthesis of anthocyanin pigments just before the leaves fall from the trees.
http://harvardforest.fas.harvard.edu/leaves/process
Leaves that get the most sunlight will develop red leaves, as the sugars inside them are baked into the red anthocyanin pigments (the same process which causes many apples to only be red on the side facing the sun as they grew).
http://www.cnn.com/2012/09/19/travel/why-leaves-change-color/index.html
The Process of Leaf Color Change. Leaves change color during the autumn because the amounts of pigments change as the leaves prepare to fall from the trees. All leaves gradually lose chlorophyll during the growing season, and this loss accelerates before leaf fall.
http://harvardforest.fas.harvard.edu/leaves/process
Tropical forests often have many deciduous trees that lose their leaves in response to drought; typically the leaves do not change color before they drop. In areas that are often cloudy for much of the autumn, with rather warm temperatures, fall colors are dull at best. This is often the case in much of Europe.
http://usna.usda.gov/PhotoGallery/FallFoliage/ScienceFallColor.html
The Science of Color in Autumn Leaves. As the days get cooler and frost is in the air, deciduous trees and shrubs put on an autumn show in all shades of red, yellow, purple, and brown. The splendor of crisp fall days and vibrant leaves brings to mind memories for nearly everyone who lives in an area where deciduous forests are the dominant vegetation. In many parts of the country, autumn leaves are an important factor in tourism. Many think that cool weather or frost cause the leaves to change color. While temperature may dictate the color and its intensity, it is only one of many environmental factors that play a part in painting deciduous woodlands in glorious fall colors.
http://usna.usda.gov/PhotoGallery/FallFoliage/ScienceFallColor.html
how leaves change colors
When photosynthesis shuts down, the chlorophyll in leaves that makes them appear green breaks down. When photosynthesis shuts down, the chlorophyll in leaves change their color.