A bijou is a mixed cocktail composed of gin, vermouth, and chartreuse. This beverage invented by Harry Johnson is called bijou because it combined the colors of three jewels: gin for diamond, vermouth for ruby, and chartreuse for emerald.
The bijou was widespread for several decades however, it disappeared after Prohibition.
Add all ingredients into a mixing glass with ice and stir until well-chilled.
Strain into a coupe glass.