Which mechanism makes leaves turn red in the fall?

Leaves turn red in the fall primarily due to the presence of anthocyanins, pigments that are produced in response to certain environmental conditions, such as cooler temperatures and increased sunlight. As chlorophyll breaks down and green color fades, these pigments become more visible. The production of anthocyanins may help protect the leaves from light damage and reduce water loss, enhancing the tree's chances of survival during winter.