Literally, rire jaune translates as laughing yellow. While it might conjure up a mouth full of yellow teeth, the meaning is actually quite different: It means laughing in a fake or forced way, to conceal unease and/or annoyance.
Which begs the question: why yellow? Why would the color yellow be associated with fake laughing?
The expression first appeared in 1640 with the linguist Antoine Oudin who wrote Il rit jaune comme farine – He laughs yellow like flour. Why yellow like flour? Well, while there is a consensus on what the expression meant at the time and still does today, there is no consensus as to what Oudin's yellow flour originally referred to.
Some believe Oudin might have referred to the tradition for actors to wear flour as make-up in those days. Actors were indeed experts at fake laughing - and yes, unprocessed flour as it was then was yellow-ish.
Others believe he might have used the color yellow as a symbol for treason. In the Middle Ages, yellow could have 2 opposite meanings depending on how bright it was: vivid yellow was associated with gold, life and the sun, while matte yellow represented the color of Sulphur, deception, dishonesty, duplicity. This is how yellow became the color of Judas, the biblical character who betrayed Christ. From this ill-famed apostle, the symbol went on to characterize anyone who should not to be trusted.
Julie riait jaune quand tu lui as dit qu’elle avait vieilli !
Julie forced herself to laugh when you told her she had aged!
Tu riras jaune quand j'aurais gagné!
You'll be laughing on the other side of your face when I win!