What are the reasons for the cool weather and colorful leaves in autumn?

It is precisely because the days are short and the nights are long that chlorophyll is decomposed during the day, and chlorophyll on leaves is decomposed into trunks and branches. After the chlorophyll on the leaves is decomposed, lutein begins to decompose and the leaves turn yellow. After lutein is decomposed, anthocyanins begin to decompose and leaves become colorful.