Pat Kiewicz wrote:

A lot of red Japanese maple varieties do that. Some varieties hold
stay red longer than others. But they all fade to a greener color
at some point during the year. Hot weather and/or shade seem to
make the red to fade more quickly.

Our Jap maple is always red. Leaves never turns green. Even in hot
(90+) weather, dry summers, wet summers, etc.

When the leaves drop in the fall, they're still red.