出典:Wikipedia
出典:『Wikipedia』 (2011/05/26 01:03 UTC 版)
Indigo dye is an organic compound with a distinctive blue color (see indigo). 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.