Kind of blue part three. The reddish-pink buds of Viper's Bugloss (Echium vulgare) morph into deep blue flowers via exquisite intermediate tones. This is characteristic of a number of species in the Boraginaceae family. Viper's Bugloss is a biennial wildflower of chalk grasslands, coastal areas and disturbed ground. For the eco minded gardener it is regularly cited as one of the top bee plants.
 As mentioned in the first of these three entries it is thought that bees may actively favour flowers of the blue-violet frequencies on the colour spectrum. Indeed there may be more to it than pigmentation alone. The journal 'Nature' published a fascinating research paper which (to quote the title) proposes that "Disorder in convergant floral nanostructures enhances signalling to bees." The researchers' findings suggest that microscopic grooves and ridges on the surface of petals can create a 'blue halo' of scattered light particles around the flower. Even on flowers that aren't blue!