expression, godan verb (-gu)
flush bright red; turn crimson
Idiomatic expression describing a face or sometimes other body parts turning vividly red, often from embarrassment, anger, or alcohol. The verb 注ぐ (to pour) metaphorically suggests color being poured onto the skin.
彼は恥ずかしさで顔に朱を注いだ。
His face flushed bright red with embarrassment.
酒を飲むとすぐに頬に朱を注
When he drinks, his cheeks quickly turn crimson.