Fast Green FCF (FD&C Green No. 3; Food green 3; C.I. 42053) is a sea green triarylmethane food dye. It is a dye used to stain proteins for IEF (isoelectric focusing) and SDS-PAGE. When bound to proteins, Fast Green FCF fluoresces near infrared (absorption maximum: 624 nm). Fast Green FCF staining is linear over a wider range of protein concentrations compared to Brilliant Blue R.