noun
the lone woman in a group
Idiom literally meaning 'a single point of red', referring to the only woman among men, often with a nuance of standing out like a bright flower.
会議室には男性ばかりで、彼女が紅一点だった。
The meeting room was full of men, and she was the only woman there.
このプロジェクトチームの紅一点
As the lone woman on this project team, she really stands out.