rire jaune

to give a forced laugh

This expression means to force a laugh when you actually feel uncomfortable, embarrassed, or upset.

Quand son chef a fait une blague sur son retard, il a ri jaune.

When his boss joked about him being late, he gave an awkward, forced laugh.

Recorded as early as 1640 by Oudin in the form 'il rit jaune comme farine.' Two theories compete: one ties yellow to the jaundiced complexion of liver-disease sufferers, who could hardly laugh sincerely; the other points to yellow's long association with treachery in European culture, Judas was traditionally depicted in yellow robes.