i-adjective
Standard color term for blue, including sky blue and deep blue. Covers a wider blue-green range than English 'blue'.
今日は空がとても青い。
The sky is very blue today.
彼女は青い目をしている。
She has blue eyes.
i-adjective
green (of fruits, vegetables, traffic lights)
Used for green objects that Japanese traditionally calls 青い, such as unripe fruit, green vegetables, and green traffic lights. Mostly archaic or fixed in modern usage.
信号が青いから渡ろう。
The light is green, so let's cross.
このトマトはまだ青い。
This tomato is still green (unripe).
i-adjective
Only when written 青い / 蒼い
Describes a face that looks pale, ashen, or sickly. Often used with 顔.
彼は顔が青い。
He looks pale.
驚いて顔が青くなった。
His face turned pale with shock.
i-adjective
Only when written 青い / 蒼い
Metaphorical extension from unripe fruit to a person who is green or inexperienced. Often used in set phrases like 青い考え.
彼はまだ青いが、やる気はある。
He's still inexperienced, but he's motivated.
そんな青い考えでは成功しない。
You won't succeed with such naive ideas.