Who in the world has ever heard the phrase “Put on your blues” ? Every manual worker and artist in France has, and they’ve probably used the expression themselves : Mets ton bleu ! It’s an expression that dates from the end of the 19th century, when the "blues" were born. Miners and other manual laborers in the Unites States had blue jeans, but in France, the bleu de travail is a whole other story.