Gamboge (/ɡæmˈboʊʒ/ gam-BOHZH, /-ˈbuːʒ/ -BOOZH) is a dark saffron yellow to partially transparent mustard yellow pigment. It is the traditional color used to color the robes of Buddhist monks and, in particular, of Theravada Buddhist monks. Physicist Jean Perrin used this pigment in 1908 to demonstrate Brownian motion.