Rangoli is a type of Hindu art. It is usually created on the floor during festivals. Rangoli can be translated to mean a row of colours.
A legend says that a king and his kingdom were in deep sadness when the son of the high priest died. Everyone in the kingdom prayed to Lord Brahma. Lord Brahma listened to the prayers and then asked the king to paint a picture of the priest’s son onto the floor so that he could bring the picture to life. From then on floor painting became a tradition. And that is why rice, flour and flowers were painted in order to give offerings to God.
In ancient India, Rangolis were created to decorate the floors of doorways within homes in order to welcome guests through the use of bright colours. This is why Rangolis is used during Diwali as it is used to welcome the guests which bring gifts to one another’s homes.
In parts of India, housewives make Rangoli pictures everyday especially when celebrating something significant such as a birth or wedding. The designs are simple geometric patterns.

Information gained from the following web sites:

www.diwalifestival.org