Why don't leaves turn gray?

Spring is green.
Sometimes yellowish-green.
Sometimes lime.
But never greenish-blue.

Spring is bright, brighter, brightening.
Light bursts forth, infiltrates the trees,
	blazes upon the meadows,
	unearths the sprouts,
and forces little buds to come out of hiding,
	pimpling the very bark of the bushes.

Chlorophyll rules in the Spring.

Full Summer is boring, by contrast: Whitest, brightest, Summer, with sky blues never seen in other seasons. Summer is lush stability, Sometimes to the point of fat, lazy, soggy stupor. Things are easy in the Summer, But it is far easier to laze in, or preferably out, of the Sun. Mañana rules in the Summer
Fall is a pastel rainbow Perfect for tackling tasks, starting anew, sloughing off the cloying coil of Summer's wide-awake hibernation. Autumn is invigorating. The leaves cooperate by sketching imaginative, inspiring backgrounds, with daily revisions, then exiting their trees, parting from the stem, with fluttering eye-massages, but always delicate, soft pastels, wise siennas, weary umbers, never intruding with the brash clammor of Spring/Summer shades. Fall falls softly, brown and crisp.
Then comes Winter to end the cycle. Nature withdraws, and the stage is set for a lively but inanimate world. Spectacular snow, as white and bright as Summer light, but illuminating only the serenity of the cold. The black heart of winter masquerades beneath the glare.
There is but one flaw in the color scheme. With the dazzling dying of warmth and growth, the frigidity of Winter, is heralded by the panoply of Autumn's fading rainbow, the leaves descend reluctantly and hesitantly, but land they must, covering the graying grass with a sea of brown. Why don't leaves turn gray?