Ponceau 4R. Molecular model of the synthetic colourant and food colouring Ponceau 4R (C20.H11.N2.Na3.O10.S3), a red azo dye which is used in a variety of food products. It has many other names, including Cochineal Red and Brilliant Scarlet. As a food additive, it is known by its E Number E124. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue), oxygen (red), sulphur (yellow) and sodium (violet).