FACT: Many native trees in Southern California are actually deciduous and do change color in the fall, but too many people have transplanted "exotic" evergreen trees from other places to propagate here, only to bitch that we "have no seasons." https://twitter.com/Aintropy/status/1317198231814787072

Western Sycamore (Platanus racemosa), a native deciduous tree to California, in fall color mode:

Western Redbud (Cercis occidentalis), another California native deciduous tree, changes from green to this wonderful magenta:

California Box Elder (Acer negundo) is yet another California native deciduous tree, which turns orange/yellow in the Fall:

Velvet Ash (Fraxinus velutina), native to California and Arizona, is a deciduous that thrives in hotter regions. It turns yellow in the Fall:

California Black Walnut (Juglans califonica), a nut-producing native, that has leaves that turn yellow in the Fall, and one local city was even named after it:

Palo Verde (Cercidium floridum) is another hot-climate deciduous that's native to CA, AZ and northern Mexico. Its leaves turn yellow: