Hilchos Lashon Hara, Opening – negative commands (14)

If he insulted the person so much that his face changed color, he also breaks the negative commandment (Vayikra 19:17), "Do not bear a sin through him." Here the Torah warns not to embarrass a Jew even when rebuking him in private - and all the more so it is forbidden to embarrass a Jew when one is not even rebuking him.

All this is in private. If it happens in public, the sages have already said he loses his share in the World to Come: "Whoever whitens the face of his fellow in public has no portion in the world to come."