During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured.This food-making process takes place in the leaf in numerous cells containing chlorophyll,which gives the leaf its green color.Along with the green pigment are yellow to orange to red pigments as well.Most of the year these colors are masked by great amounts of green coloring.But in the fall,because of changes in the length of daylight and changes in temperature,the leaves stop their food-making process.The chlorophyll breaks down,the green color disappears,and the yellow to orange to red colors become visible and give the leaves part oftheir fall splendor.The best time to enjoy the autumn color would be on a clear,dry,and cool day.