The relationship between the flower color and flavonoid composition of petals was investigated in 16 cultivars of Catharanthus roseus. Eleven anthocyanins, including two new anthocyanins (hirsutidin 3-galactoside and rosinidin 3-galactoside) and 7-methylcyanidin 3-galactoside, which has never been reported in C. roseus, were identified from the flowers of Catharanthus roseus along with two known caffeoylquinic acids and ten known flavonol glycosides. Regarding the flower color from red to purple-violet, decreases in the hue values (b*/a*) of these cyanic petal colors excluding the eyes were suggested to be responsible for increasing the ratio of flavonol glycosides, decreasing total anthocyanins, and controlling hydroxyl and methoxyl patterns of the B-ring in anthocyanins.