https://phys.org/news/2018-05-blackcurrant-dye-hair-safer-sustainable.html

The researchers extracted and purified a group of pigments from the skins called anthocyanins, which commonly produce colors ranging from pink to violet in fruit, vegetables and flowers. The team used these pigments in a dye paste and applied it to bleached human hair, producing a vivid blue color, and they could produce reds and violets by modifying the dye formulation. There were no significant changes in these new hair colors after 12 shampoos. After analyzing how these natural compounds fix to the hair, they concluded that anthocyanin-based blackcurrant dyes are comparable to conventional colorants and could become an important component in dye mixtures used to produce a variety of hair colors and shades.

                                                            
                                    
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                                    Paul M. Rose et al. Application of Anthocyanins from Blackcurrant (Ribes nigrum L.) Fruit Waste as Renewable Hair Dyes, Journal of Agricultural and Food Chemistry (2018). DOI: 10.1021/acs.jafc.8b01044