Have raised a few acorns to oak plants at home last winter, and also planted acorns at the cabin.

All of them have green leafs, but one has a different colour.

Three other plants in the garden have normal leaves as the ones already planted in the vicinity of the cabin.

This one was planted as an acorn in my garden last fall. And it seems to do OK, despite of the colour. All the trees where I collected acorns are green.

Does anyone know the reason for the colour?

"But some Hurricanes were deliberately broken up and buried after the war so the Soviets did not have to pay back the United States. Under the Lend-Lease legislation, the USSR was required to pay for any donated military equipment that remained intact after hostilities ended."

Well, of course, Russians cheated then, as always.
https://www.bbc.com/news/world-europe-65955365