Leaves in the spring and summer are mostly a pretty uniform green color. For that, you can thank the chemical compound known as chlorophyll. Chlorophyll is responsible for the process of photosynthesis, which takes sunlight and converts it into the sugars needed to sustain the tree. There are a variety of other chemical compounds, with characteristic colors other than green, always present in the leaves; however, the green chlorophyll dominates and masks your ability to see them.