Indigo dye
Indigo dye is an organic compound with a distinctive blue color. Historically, indigo was a natural dye extracted from plants, and this process was important economically because blue dyes were once rare. Nearly all indigo dye produced today several thousand tons each year is synthetic. It is the blue of blue jeans.
Uses:
The primary use for indigo is as a dye for cotton yarn, which is mainly for the production of denim cloth for blue jeans. On average, a pair of blue jean trousers requires 3–12 gm of indigo. Small amounts are used for dyeing wool and silk.
Indigo carmine, or indigotine, is an indigo derivative which is also used as a colorant. Approximately 20M kilograms are produced annually, again mainly for blue jeans.[ It is also used as a food colorant, and is listed in the United States as FD&C Blue No. 2, and in the European Union as E Number E132.
