Indigofera genera

The blue dye indigo, derived from the plant Indigofera tinctoria, has been used in India for thousands of years. Traders introduced it to the Mediterranean area and then to Europe. Tyrian purple, a natural dark purple dye obtained from the mucous gland of a Mediterranean snail of the genus Murex, was a symbol of royalty before the collapse of the Roman empire. Alizarin, a bright red dye obtained from madder root Rubia tinctorum), a plant native to India and northeastern Asia, has been found in cloth entombed with Egyptian mummies. 

In this ancient process as many as 10,000 molluscs were used to produce one gram of the dye. In other parts of the world blue dyes were generated by fermentation of plants of the genus Indigofera and also of the European woad plant. ... 

Indigo Abluevatdye, CieHioN202. It occurs as the glucoside Indlcan in the leaves of plants of the genus Indigofera, from which it was formerly extracted. It is now made synthetically. 

Indigo in -di- go [It dialect, fr. L indicum, fr. Gk. indikon, fr. neuter of indikos Indie, fr. Indos India] (1555) n. C16H10N2O2 (molecular weight, 262.26). Dark blue, transparent dye produced either by fermentation from the genus, Indigofera, indigenous to the Far East, or synthetically. 

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