Red flowers have evolved repeatedly across angiosperms and are frequently examined in an ecological context. However, less is known about the biochemical basis of red colouration in different taxa. In a recent study published by AoB PLANTS, Ng and Smith examined the biochemical basis of red flowers in the tomato family, Solanaceae. They show that red-flowered species have converged on the same floral hue using either the sole production of red anthocyanin pigments or, more commonly, the dual production of purple or blue anthocyanins and orange carotenoid pigments. The use of blue anthocyanins in red flowers appears to differ from other groups, and suggests that the genetic changes underlying evolutionary transitions to red flowers may not be as predictable as previously suggested.
Julienne Ng, Stacey D. Smith, 2016, 'How to make a red flower: the combinatorial effect of pigments', AoB Plants, vol. 8, p. plw013 http://dx.doi.org/10.1093/aobpla/plw013