The plant extract serves not only as a good source of bioactive compounds but also as natural pigment that can be applied as colourants in food and pharmaceutical products. The aim of this study were to determine the anthocyanin content of Garcinia mangostana peel extract (GMPE), Clitoria ternatea extract (CTE) and Syzigium cumini extract (SCE) in relation to their antioxidant activity and their colour properties. The antioxidant activities related to the phenolic constituents including anthocyanin content were determined based on the EC50 of DPPH radical scavenging activity and Ferric Reducing Antioxidant Power (FRAP) assay. The colour properties of the plant extracts were measured based on their degradation index (DI), indices of polymeric colour (PC) and colour density (CD). GMPE showed higher FRAP value and lower EC50 value which were 79.37 mmoles/g and 0.11 mg/ml, respectively, as compared to SCE extract with FRAP value, 25.66 mmoles/g and EC50 value, 0.22 mg/ml. Total monomeric anthocyanin (tmAcy) exhibited a strong correlation between FRAP assay (r2 = 0.998) and DPPH assay (r2 = 0.859). GMPE showed high CD (1.63 AU), moderate PC (0.18 AU) but low in DI (1.19 AU) while SCE exhibited low in CD (0.55 AU) and PC (0.07 AU) but moderate DI (1.26 AU). CTE exhibited high in DI (5.39 AU) and PC (0.19 AU) but moderate in CD (0.55). Hence, it can be concluded that colour pigment obtained from GMPE exhibited high antioxidant activity and better colour properties as compared to SCE and the strong correlation between tmAcy and two antioxidant activity assays which are FRAP and DPPH indicated that monomeric anthocyanin plays a major role in antioxidant activity of these plant extracts.