Vermilion, powdered red lead, applied as a dot on the forehead, like the regular "bindi or in the parting of the hair by all suhagans. It is worn by married women, as a visible expression of their desire for their husbands" longevity. Traditionally therefore, widows did not wear vermilion.
Red is the colour of power. Vermilion is thus a symbol of the female energy of Parvati and Sati. Sati is believed to be the ideal wife, one who gave her life for her husbands" honour. Every Hindu wife is supposed to emulate her. It is believed that Parvati protects all those men whose wives apply vermilion to their hair-parting.
Sindoora is applied for the first time to a woman during the marriage ceremony when the bridegroom himself adorns her with it . Sindoora-dana, as this part of the marriage ceremony is called, is important today but is not mentioned before the Grihasutras? indicating that it is a relatively new practice.