Green S is a green synthetic coal tar triarylmethane dye with the molecular formula C27H25N2O7S2Na. As a food dye, it has E number E142. It can be used in mint sauce, desserts, gravy granules, sweets, ice creams, and tinned peas. Green S is prohibited as a food additive in Canada, United States, Japan, and Norway. It is approved for use as a food additive in the EU and Australia and New Zealand. Green S is a vital dye, meaning it can be used to stain living cells. It is used in ophthalmology, among fluorescein and rose bengal, to diagnose various disorders of the eye's surface. Green S may cause allergic reactions and is one of the colorants that the Hyperactive Children's Support Group recommends to be eliminated from the diet of children.