Naphthol Green B is a coordination complex of iron that is used as a dye.Naphthol Green B is the sodium salt of Naphthol Green Y (C.I. 10005). The organic ligands each bind to iron as bidentate ligands through the nitrogen and the anionic phenoxide groups. It contains a 5-(oxidoimino)-6-oxo-5,6-dihydronaphthalene-2-sulfonate.