Blue is the last color to appear in the natural world, and the last to be developed and produced by Humans in the Anthropocene. Color systems used by liverworts (furanoflavylium), mosses and ferns (3-deoxyanthocyanins), and angiosperns (anthocyanins) are chemically identical species with the same sequence of chemical reactions, but only the anthocy... See more

Most of the blue colors that do not involve metals are achieved from intramolecular copigmentation. According to Andersen and Jordheim [52] more than 65% of the anthocyanins reported up to 2006 with their structures identified are acylated. In some plants the same anthocyanin can give red and blue. The presence of acylated anthocyanins is a... See more

“blue coloration by intermolecular co-pigmentation alone is not common, and when it occurs, it is usually the result of co-pigmentation of anthocyanins with glycosylated flavonols and flavones”

Copigmentation is the result of the non-covalent interactions with different species of the flavylium multistate, in particular flavylium cation and quinoidal bases, with other compounds, mainly phenolic acids and flavonoids [8,43,45]. The copigmentation is achieved by π−π stacking as shown in Scheme 8. Many examples of copigmentation can be found... See more

In the case of the blue color two main strategies have been used by plants and studied in detail. They involve acylation of the sugars to allow intramolecular copigmentation and complexation with metals

In conclusion, the blue color only appeared many million years after the first plants color systems and only through the anthocyanins, Fig. 3.

When the evolution of plants is compared with the geologic time, it can be concluded that the appearance of the blue color in angiosperms occurred million years after the first plants exhibiting greens (chlorophyll), yellows and particularly reds (in the form of quinoidal bases) appearing in liverworts (auronidins), mosses and ferns... See more

In general, the blue color is only achieved when the anionic quinoidal base is formed, which occurs for pH values near the neutrality. However, this is not a general behavior for all anthocyanins. In cyanidin, Fig. 3, the anionic quinoidal base is not blue (only the dianionic quinoidal base achieved for basic pH values is blue). In this case, the... See more

Some authors consider the possibility of Tekhelet, the most sacred of biblical colors in Judaism, be a blue or purple dye derived from Tyran purple [29,30]