Hair colouring was done by men and women to enhance their looks or hide white strands, according to Victoria Sherrow's Encyclopedia of Hair: A Cultural History. Ancient civilisations used dyes made of cassia bark, leeks, leeches, charred eggs, henna — still commonly used across the MiddleEast and India. Ancient Greeks favoured gold and red-gold shades, associated with Aphrodite, the goddess of love, health and youthfulness.
Likewise, high-class Greek and Roman prostitutes opted for blonde hues to suggest sensuality. It wasn't until the Middle Ages in Europe that hair dyeing began shifting into a predominantly female habit. Bleaches, often made with blended flowers, saffron and calf kidneys, were particularly in vogue, although Roman Catholics associated blond hair with lasciviousness. Red dyes, often a mix of saffron and sulphur powder (which could induce nosebleeds and headaches) was popularised during the 16th-century reign of Elizabeth I of England. In the 18th century, European elites favoured perfumed white and pastel powders made from wheat flour dusted lightly onto natural hair and wigs.
Although most hair dyes were composed of plants and animal products, the evolution of the practice also saw the use of dangerous, even lethal methods to change hair colour: lead combs to darken it, or sulphuric acid to lighten it. (via CNN)