What makes our Hands blue?

Indigo dye is an organic compound with a distinctive blue color. Historically, indigo was extracted from plants, and this process was important economically because blue dyes were once rare. Nearly all indigo produced today - several thousand tons each year - is synthetic. It is the blue of blue jeans and of course of our hands.

And this is this lovely flower that can make your jeans blue.

For more information just check the internet.