The colour stability of natural blue dye extracted from Clitoria ternatea L. in poly(acrylamide-co-acrylic acid) coating film by Abidin, Zul Hazrin Zainal, Manah, N.S.A., Hadi, A.N., Saugi, Nur Susilawati, Fuad, F.A., Mazni, N.A., Hassan, H.C., Careem, Mohamed Abdul, Arof, Abdul Kariem