Blueberries’ blue is just skin deep, depending on structure not pigments

Despite their name and appearance, blueberries do not contain any blue pigments. New research attributes their blue hue to interactions between light and the nanostructures found in their natural waxy coating. Further investigation of this wax in the laboratory may help inspire new sustainable, self-cleaning and -repairing optical biomaterials.

Several types of fruit, including varieties of grapes, plums and damsons, feature a waxy epicuticular coating known as bloom that protects them from predators and pathogens and helps make them waterproof and self-cleaning. While these fruits are rich in dark red anthocyanin pigments, when their bloom is intact they appear blue. Vertebrates can see blue light well and such fruits are attractive to them, but blue-reflective pigments are costly to create. Structural colouration, commonly seen in the feathers of brightly coloured birds, relies on microscopic structures in a surface changing how light is reflected, and can be a less costly way of appearing blue.