The Tilaka is normally a vermilion mark applied on the forehead. This mark has a religious significance and is a visible sign of a person as belonging to the Hindu religion. The Tilaka is of more than one color although normally it is vermilion. It also does not have any standard shape and form and is applied differently by members of different Hindu sects and sub-sects.
It is applied as a 'U' by worshippers of lord Vishnu and is red, yellow or saffron in colpur. It is made up of red ochre powder (Sindhura) and sandalwood paste (Gandha). Worshippers of lord Shiva apply it as three horizontal lines and it consists of ash (Bhasma). Soot (Abhira) is also used as a pigment for applying a Tilaka.
Literally, Tilaka means a mark. Sindhura which is also used to describe a Tilaka means red and Gandha which is also a term for Tilaka means pleasant odour. Hence, Tilaka normally connotes, a red mark with a pleasant odour.
Some scholars have seen the red colour as a symbolism for blood. We are told that in ancient times, in Aryan society, a groom used to apply his blood, on-his bride's forehead as a recognition of wedlock. The existing practice among Indian women of applying a round shaped red Tilaka called Bindiya or Kumkum could be a survival of this.