In Russian, there are a lot of peculiar color names, one of them being цвет детской неожиданности, literally, "baby's surprise" or "child's surprise".
This is a shade of yellow that a newborn baby's poo has. Most sources put it as #F7F21A or close to it (https://get-color.ru/#F7F21A), but of course different people use it to call different shades, from greenish-yellow to beige.
Unlike other vague color terms calqued from French, this one is actually in wide use, and most people are familiar with it. Of course, it's mostly used humorously. You would use it to describe something you don't particularly like, like the color of a room in a cheap motel, or something like that.
Most Russian sources trace its etymology to variations of this anecdote:
Soon after queen Marie Antoinette had given birth to her soon, a lot of courtiers gathered to pay their respects to the newborn and his mother. As she was demonstrating the baby, it relieved itself on its swaddling clothes. The queen smiled and said "Look at the color of these clothes!". The next day, the courtiers showed up at the court wearing the same color, which they called "Dauphin's surprise". It became a fad in Paris and gave name to a certain shade of yellow.
(The last source attributes this color to "brothers Goncourt's diaries")
I was trying to find if it was a real story, but all the sources I could find were either in Russian or clearly authored by Russian speakers.
I don't speak French, but I can barely make heads or tails of a French text because I do speak some Italian. Googling for surprise du Dauphin, surprise du bébé or surprise de l'enfant didn't give me any promising results, and neither did English translations of these queries.
Does French have, or has it ever had some variation of "baby's surprise", "Dauphin's surprise", "child's surprise", or something like this as an idiomatic name for a shade of yellow?