Brilliant Blue FCF (Brilliant Blue FCF, FD&C Blue No. 1, D&C Blue No. 4, Acid Blue 9, Alzen Food Blue No. 1, Atracid Blue FG, Erioglaucine, Eriosky blue, Patent Blue AR, Xylene Blue VSG, diamond blue FCF, diamond blue, E133) is a synthetic dye of blue color. It can be mixed with tartrazine (E102) to produce various shades of green. Chemical formula C37H34N2Na2O9S3.
As a dye, it is often used in ice cream, sweets and beverages. It is also a part of creams, shampoos and other cosmetic products.
It was previously banned in the EU, the US and a number of other countries. The ban has now been lifted.