In article 1125404635.052824.6470
@g14g2000cwa.googlegroups.com, tomkanpa said...

What would cause the red leaves of a Japanese Maple to turn green?
Is this a permanent change in color??

It's probably temporary, meaning the leaves will emerge red
again next spring.

My A. palmatum tends to green up a bit by late summer, if the
season has been evenly temperate and moist. In years like the
current one, where (in Pennsylvania) we experienced a period of
heat and drought, the leaves remain red. Toward the end of
autumn, regardless of the summertime color of the foliage, the
leaves turn a beautiful scarlet before they fall.

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Brian E. Clark