The betalains are divided into two groups : the betaxanthins (yellow colour) and the betacyanins (red to violet colour). A betalain with blue colour does not exist, so the obtention of a cactus with blue blooms seems to be impossible.The blue colour of the Wittia amazonica petal tips seems to be due to the structure of the blooms' surface cells (reflection of the rays ?), and not to pigments.
