Benzopyran, also called chromene, is a ring made of a benzene ring fused with a pyran ring. Flavonoid pigments, including anthocyanins, are all built on this chromene skeleton, which is why plants get their red, blue and purple shades from this family. Carotenoids are built from isoprene units instead, and chlorophylls and bilins are built on pyrrole rings, so they do not fit here. That leaves anthocyanins and flavonoids as the pigments with the benzopyran backbone.