Maybe the anecdote about more highly colored leaves in winter (which I've heard many times), is because homes often receive more direct sun in the winter, as the sun sinks closer to the horizon on its daily arc. My house has south facing windows- in the summer hardly any sun makes it inside more than a foot from the window, in winter it is much brighter, despite the shorter days. And hence more leaf color.
Temperature Tolerance Footnote
Good point, Mark!!!