Black walnut drupes contain juglone (5-hydroxy-1,4-naphthoquinone), plumbagin (yellow quinone pigments), and tannin. Black walnuts make a orange-brown dye. The liquid (dye) obtained from the inner husk becomes increasingly darker over time, as the outer skin darkens from light green to black. Juglone is an isomer of lawsone, which is the staining compound in the henna leaf.