Why do the leaves change color?
Actually, the orange, yellow and brown colors are already in the leaves even during the summer time. However, you can't see those colors because the green color is so dominant. The green color comes from chlorophyll, a chemical that helps plants use sunlight to break down water and carbon dioxide into sugars- a food source for plants.
Less and Less Daylight Starts The Change:
So, every Autumn as there is less and less sunlight each day the chlorophyll in the leaves diminishes, allowing the green color to fade and the oranges, yellows and browns to show. However, most reds and purples are created in Autumn due to certain weather conditions.
The Role Of Weather:
The weather doesn't necessarily change the colors, but it impacts the brilliance of the colors. Warm and sunny days with cool (but not freezing) nights is the perfect weather to help bring out the reds and purples. So, when the leaves start to change colors, you'll want sunny days and cool nights to see more red, purple and crimson. Soil moisture can play a role too, as droughts can postpone the peak of Fall colors by a few of weeks. But we've had record amounts of moisture this year, and I already see the leaves are changing colors and will continue to change more and more each day over the next week or two.