Why do leaves turn beautiful shades of red, orange and yellow in the fall? First of all, although commonly heard this time of year, it is actually incorrect to say that they 'turn' colors. You may be surprised to learn that they contain most of these colors within them from the beginning.
Every year when fall arrives and reveals itself in the trees around me, I think of Mr. Linton's 8th grade science class, where I learned that leaves don't change to the golden hues of fall. It's the presence of chlorophyll in the leaves during the spring and summer months that turns them green, and masks the other colors. As you probably know, plants feed themselves through the process of photosynthesis, whereby sunlight is converted to energy in the form of sugar. Chlorophyll is a pigment that absorbs red and blue light for the energy conversion process of photosynthesis, repelling green light back to our eyes.
According to Science Made Simple, which is a great science reference for kids (adults may find some interesting facts here too), carotene, which are pigments responsible for orange colors, and xanthophyll (yellows) appear when photosynthesis subsides in autumn. Reds however, are usually produced in the fall by anthocyanins, pigments that result from trapped glucose in the leaves.
The site also outlines a fun experiment to conduct with kids, in which you can actually separate the colors in a green leaf!