blêmir

To turn pale or ashen, typically from fear, shock, or anger — a more literary/dramatic verb than the everyday pâlir, often used in narrative writing to signal a strong emotional reaction.

• Il a blêmi en apprenant la nouvelle. — He turned pale on hearing the news.
• Elle blêmit de rage devant cette injustice. — She went pale with rage at this injustice.
• Son visage blêmit soudain quand il vit l'accident. — His face suddenly went pale when he saw the accident.

It's a stronger, more literary word than pâlir — reach for pâlir in ordinary conversation and save blêmir for descriptive or dramatic writing where a sharper image is wanted.