Most of us have heard that the "autumn colors" of a leaf are always there, hidden by the green chlorophyll. All of these leaves came from the same tree. Why are some yellow, while others are red?
These are leaves from a Chinese Tallowtree, an invasive species in Florida. The yellow and orange colors in autumn leaves is from carotenoid pigments, which are always in the leaf. The red colors are anthocyanin pigments which are produced when excess sugar is trapped in the leaf when the tree starts the process of abscission, sealing off the leaf and weakening the base so it will break and the leaf will fall.