Why Do Leaves Change Color? So Many Colors. Why are the leaves on trees different colors? What makes them change color? Making Food. Leaves use sunlight, water, and air to make food for the tree. This way of making food is called photosynthesis. A chemical that helps leaves make food also makes them green.Photosynthesis is important to animals as well as plants. Some animals eat plants. Other animals eat those animals. Without photosynthesis, neither kind of animal would have food. Summer. Summer is playtime. For the leaves of many trees, however, it's work, work, work! The Sun is shining. The leaves are making food for the trees. The trees store any extra food deep inside. The stored food will help them get through winter. Leaves are green in summer because they are making food. Leaves also have orange, yellow, or brown colors inside them. During summer, those other colors are hidden by the green color. Fall. Many places get colder in fall. The days get shorter, and the nights get longer. Trees get less sunlight, so photosynthesis slows down.Over time, leaves stop making the green chemical, so they lose their green color. When that happens, the hidden orange, yellow, and brown colors start to show. Leaves also start making a red color at this time. Once it gets cold enough to freeze at night, the trees drop their leaves. They do this to keep themselves safe. If the leaves freeze while still on the trees, the trees can be hurt. Winter. Trees that drop their leaves are bare in winter. They use the stored food to get through the cold days and colder nights. Spring. Spring comes before long. Ice and snow melt, and the rains come. The Sun shines, and tiny leaves grow from branches. Once again, the leaves use sunlight, water, and air to make food. The cycle begins again.