September 18, 2013 @ LiveScience
Why do some plants have these purple parts?
Green plants contain a lot of the pigment chlorophyll. Because chlorophyll molecules are very good at soaking up blue and red light — but not so good at absorbing green light — plants containing a lot of chlorophyll appear green to the human eye. Plants that appear purple, blue or red contain a higher concentration of anthocyanin than chlorophyll. Anthocyanin is a pigment adept at absorbing green light, but less skilled at absorbing red, blue or purple light.