Fast green FCF is an organic sodium salt having 2-{(4-{ethyl[(3-sulfonatophenyl)methyl]amino}phenyl)[4-{ethyl[(3-sulfonatophenyl)methyl]iminio}cyclohexa-2,5-dien-1-ylidene]methyl}-5-hydroxybenzene-1-sulfonate as the counterion. Used as a substitute for Light green SF yellowish in Masson's trichrome as it is less likely to fade, and is more brilliant in colour. Also used as a food colouring agent. It has a role as a fluorochrome, a histological dye and a food colouring. It contains a Fast green FCF(2-).
