This is the 9773rd most frequent Polish word.
zielone
Green.
In this sentence, 'zielone' is an adjective describing the color of the apple.
Mam zielone jabłko.
I have a green apple.
Here, 'zielone' describes the color of the traffic light, indicating permission to proceed.
On ma zielone światło na skrzyżowaniu.
He has a green light at the intersection.
In this idiomatic expression, 'zielone' implies approval or permission.