I worked out in the back yard for a while this afternoon and picked this twig from our Euonymus alatus (Burning Bush). It was a south facing branch in full sun but most unusual to color this early in the fall. I was unable to detect any damage or infestation which may have been a factor nor any other branches showing color. The bush has been in our yard for some 30 years and don’t recall ever seeing this happen. Wikapedia provided the following information: Euonymus alatus, known variously as winged spindle, winged euonymus or burning bush, is a species of flowering plant in the family Celastraceae, native to central and northern China, Japan, and Korea.This deciduous shrub grows to 2.5 metres (8 ft 2 in) tall, often wider than tall. The stems are notable for their four corky ridges or "wings". The word alatus (or alata, used formerly) is Latin for "winged", in reference to the winged branches. These unique structures develop from a cork cambium deposited in longitudinal grooves in the twigs' first year, unlike similar wings in other plants. The leaves are 2–7 centimetres (0.79–2.76 in) long and 1–4 centimetres (0.39–1.57 in) broad, ovate-elliptic, with an acute apex. The flowers are greenish, borne over a long period in the spring. The fruit is a red aril enclosed by a four-lobed pink, yellow or orange capsule.
The common name "burning bush" comes from the bright red fall color.