Think of the moment the light at a crossing turns green. Nothing pushes the cars forward. The block in front of them is simply lifted, and now they may go. That feeling of being unblocked is what travels into every other use of the words.
可以想成路口那盞燈剛轉綠的瞬間。沒有人推車子往前，只是擋在前面的限制被拿掉了，現在可以走。green light 最有用的地方就是這個「解鎖」的感覺。它本身不代表稱讚，也不代表催促，只代表「不再擋著你了」。所以後來只要有人在等誰點頭，英文都借這盞燈來說。
From the word’s history
Wiktionary traces the words to the standard red-green colour scheme of traffic lights and railway signals: red stops, green releases.
Wiktionary 的詞源說明指出，這個詞來自交通號誌與鐵路號誌固定的紅綠配色：紅色擋下、綠色放行。所以核心畫面確實是從真實的燈號來的，不是後人補上的比喻。
Wiktionary entry for green light, supplied in this packet (kaikki:3f6f69a190036ae4:1009342755:20928)
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