Photos courtesy of 123rf.com
In the process of dying bluejean-denim indigo blue, the synthetic indigo-dye first turns the cotton yarn a bright green, then as it dries the oxidation process turns it dark indigo blue, a process that is much the same as the oxidation of iron. See how it's done on "Factory Made" on the Science Channel today: http://science.discovery.com/videos/factory-made-full/
