Catalysis of the reaction: (E)-4-coumaroyl-CoA + an anthocyanidin 3,5-di-O-beta-D-glucoside = an anthocyanidin 3-O-beta-D-glucoside 5-O-beta-D- + CoA. Caffeoyl-CoA can also act as an acyl donor.
anthocyanin 5-aromatic acyltransferase activity