Why do leaves change color every autumn season?

Leaves change color in autumn because of changes in light and temperature. As days get shorter and temperatures drop, trees prepare for winter by stopping the production of chlorophyll, the green pigment responsible for photosynthesis. As chlorophyll breaks down, it reveals yellow and orange pigments called carotenoids that were always present in the leaves but masked by the green color. The bright reds and purples come from anthocyanins, which are actually newly produced as sugars become trapped in the leaves when trees seal off their connection to branches. Once this process is complete, the leaf dies and falls. The intensity of fall colors depends on weather conditions, with cool nights and sunny days producing the most vivid displays.