Is indigo safe for hair

Indigo is a natural dye that can be very safely used for coloring hair. In fact the same indigo is used for dying blue jeans. 

Indigo can make your hair blue-black if you already have dark hair, and it can make your hair bright blue if your hair is gray. However, indigo is a natural organic dye and is safe. Most hair dyes contain ammonia, PPD, and other dangerous chemicals that can cause allergic reactions or can even cause cancer. Indigo, when mixed with henna, gives brown color. Indigo is very safe for hair.