Colouring your hairs has been a huge trend for god knows how long. If you thought this was something started by the fashion industry you are probably wrong people have been colouring their hairs since the age of Neanderthals !!!
Obviously, there were no hair colours back then but still, the ancient people managed pretty well. It was common to use different plant and animal extracts to colour their hairs, clearly for reasons other than just looking good.