We currently know little about the evolution of flower colour when multiple pigment families are present. Ellis and Field examined the patterns of evolutionary transitions between anthocyanin-pigmented (red, pink, blue and purple) and yellow flowers in the tribe Antirrhineae.
A phylogenetic comparative analysis points to selection for either yellow or anthocyanin pigmentation at different times. Nevertheless, these transitions are constrained to move through an unpigmented intermediate step. These findings suggest fluctuating selection favouring flowers with a single pigment over those with zero or two pigments.