noun
green traffic light
Literal traffic signal meaning; the green light that permits vehicles or pedestrians to proceed.
青信号になったら渡りましょう。
Let's cross when the light turns green.
Idiomatic use: approval or permission to start something, often in business or project contexts.
上司からプロジェクトに青信号が出た。
We got the green light from the boss for the project.