IUPAC Name: 2-(3-hydroxy-1H-indol-2-yl)indol-3-one Synonyms: INDIGO, Indigotin, 482-89-3, Indigo Blue, Vat blue 1, Cystoceva, Diindogen, Pigment Blue 66, Vulcafix Blue R, Indigo Pure BASF, Indigo Ciba, Indigo Synthetic, Synthetic Indigo, Indigo J, Indigo N, Indigo P, Indigo Powder W, Vulcafor Blue A, Vynamon Blue A, Indigo VS