Ponceau 3R ( C.I. 16155) is an

azo dye Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C−N=N−C l ...

that once was used as a red

food colorant Food coloring, color additive or colorant is any dye, pigment, or substance that imparts color when it is added to food or beverages. Colorants can be supplied as liquids, powders, gels, or pastes. Food coloring is commonly used in commercial ...

.{{cite journal, title=A Global Perspective on the History, Use, and Identification of Synthetic Food Dyes, author1=Sharma, Vinita, author2=McKone, Harold T., author3=Markow, Peter G., journal=Journal of Chemical Education, year=2011, volume=88, issue=1, pages=24–28, doi=10.1021/ed100545v, bibcode=2011JChEd..88...24S It is one of a family of Ponceau (French for "poppy-colored") dyes.

References

Food colorings Azo dyes Organic sodium salts Naphthalenesulfonates 2-Naphthols