It's fall in North Texas and the leaves are changing color. This occurs as the weather turns cooler combined with a decrease in daylight.
When trees in North Texas begin to experience cooler weather, high temperatures in the 60s, it is a signal for them to stop sending water to their leaves. At the same time, the decreasing daylight leads to a stop in photosynthesis.
Photosynthesis is a chemical reaction that takes place within the leaves that converts sunlight to a source of food energy for the tree. As photosynthesis stops, the production of chlorophyll stops. This leads to a change in the color of the leaves. The green fades away, leaving the yellow, red and orange colors.