It's been a great year for red leaf color here in the Eastern U.S. Very minimal cool nights followed by a LOT of warm sunny days seem to have resulted in much more intense late reds than usual.
It's been remarkable warm now for weeks, so anthocyanin production must be unusually high. (The red and purple pigments, in fall, are produced using sugars from photosynthesis - in real time - and sequestered in the vacuoles of leaf cells).
Our oakleaf hydrangeas are brilliant right now, as are all the feral Bradford pears around campus and the neighborhood.
And the last blueberry leaves are crimson, along with Clethra alnifolia (Coastal Sweet Pepperbush) - I've never see it so vivid.