Purple. Pigments in pitaya are mainly anthocyanins and betacyanin, so dried pitaya juice is purplish red. According to the ancient book Puji Fang, pitaya is rich in nutrition, which has the functions of preventing constipation, promoting eye care, lowering blood sugar, lowering blood lipid and lowering blood pressure. Because it contains anthocyanins, it also has the functions of promoting gastrointestinal digestion, preventing anemia, whitening skin and preventing dark spots.