A 2:1 mixture of: 4-(7-hydroxy-2,4,4-trimethyl-2-chromanyl)resorcinol-4-yl-tris(6-diazo-5,6-dihydro-5-oxonaphthalen-1-sulfonate and 4-(7-hydroxy-2,4,4-trimethyl-2-chromanyl)resorcinol bis(6-diazo-5,6-dihydro-5-oxonaphthalen-1-sulfonate