in Thoreau’s Journal:

The brilliant autumnal colors are red and yellow and the various tints, hues, and shades of these. Blue is reserved to be the color of the sky, but yellow and red are the colors of the earth flower. Every fruit, on ripening, and just before its fall, acquires a bright tint. So do the leaves; so the sky before the end of the day, and the year near its setting. October is the red sunset sky, November the later twilight. Color stands for all ripeness and success.