Fall is my favorite season. I know this doesn’t make me unusual, fall has a lot going for it. The crisp, cool air comes as a pleasant surprise every year, a relief from the oppressive heat. The crunch of dead leaves, the mild, early evenings. Halloween, cider, caramel apples, hay rides and corn mazes.

Above all else what comes to mind with fall are the spectacular colors. Fall has a distinctive palette: rust, orange, brown and yellow, the colors of those dead crunching leaves, going out in a blaze of glory.
And I do love the leaves, though the collected windfalls never seem as bright as they were just before letting go. But when I think of fall color, the colors I anticipate are the colors of the sky.

The sky has a particular, specific shade of purple that only occurs in the fall. I’m never able to capture it with a camera. It’s probably partly caused by the change of the sun’s position. It’s probably partly a unique filtering of the light that only occurs briefly when the trees are full of curled shrinking leaves.

The main cause of the purple skies is the human eye. It’s not the color of the sky that changes, it’s the comparative color as demonstrated with paper squares by color theorist Josef Albers. It’s a color that only exists when the maple trees have erupted in yellow, transforming the clear blue sky into something new.

Our maples are still green, but a few other trees have started to take the hint, and the late afternoon sun today filtered in against storm clouds to produce a strange glowing grey. It’s not quite the perfect purple sky, but it still feels remarkable, and portends change more loudly than the crash of leaf piles.