Hair coloring

Hair coloring or hair dyeing is changing the color of hair. Common reasons are to cover gray hair, to change to a color that a person likes better, and to return the hair to its normal color after it has been badly changed by hairdressing or sun bleaching. The 1661 book Eighteen Books of the Secrets of Art & Nature explained ways of coloring hair black, gold, green, red, yellow, and white .

Types of hair coloring
The four common types of hair coloring are permanent, demi-permanent (sometimes called deposit only), semi-permanent,  and temporary.“Hair Preparations,” Ullmann’s Encyclopedia of Industrial Chemistry. Wiley-VCH, Weinheim (2006). 

References

Other websites
How Stuff Works "How Hair Coloring Works"

Category:Hair
Category:Cosmetics