Diodorus Siculus, a Greek historian, described in detail how Celtic people dyed their hair blonde: "Their aspect is terrifying... They are very tall in stature, with rippling muscles under clear white skin. Their hair is blond, but not naturally so: they bleach it, to this day, artificially, washing it in lime and combing it back from their foreheads. They look like wood-demons, their hair thick and shaggy like a horse's mane. Some of them are clean-shaven, but others—especially those of high rank—shave their cheeks but leave a moustache that covers the whole mouth...". This practice continued in some parts of Britain long after the Fall of the Western Roman Empire, particularly in Wales, where Llywelyn Ap Gruffudd was described in an elegy by Gruffudd ab yr Ynad Coch to have blonde hair: "...Not since Camlann has there been such weeping, Gone is our mainstay, his golden hair, stained with a death blow...".
Portrait of Lafayette in 1830, aged 73, with pitch-black hair.
The dyeing of hair is an ancient art that involves treatment of the hair with various chemical compounds. In ancient times, the dyes were obtained from plants. Some of the most well known are henna (Lawsonia inermis), indigo, Cassia obovata, senna, turmeric and amla. Others include katam (buxus dioica), black walnut hulls, red ochre and leeks. In the 1661 book Eighteen Books of the Secrets of Art & Nature, various methods of coloring hair black, gold, green, red, yellow, and white are explained. The development of synthetic dyes for hair is traced to the 1860s discovery of the reactivity of para-phenylenediamine (PPD) with air. Eugène Schueller, the founder of L'Oréal, is recognized for creating the first synthetic hair dye in 1907.In 1947 the German cosmetics firm Schwarzkopf launched the first home color product, "Poly Color".[non-primary source needed] Hair dyeing is now a multibillion-dollar industry that involves the use of both plant-derived and synthetic dyes.