The haldi is a prewedding ritual common at traditional Indian weddings. It is celebrated on the wedding day or one day prior to the wedding day and is usually a close-knitted event. The closest family, relatives and friends come together on this auspicious occasion to apply turmeric paste (haldi) on the bride and groom’s face and body. Turmeric has a very auspicious significance in all Indian weddings. The color of turmeric is identified in Indian culture as a color of prosperity. Although not mandatory, it is customary to wear yellow clothes during this function.
More information can be found here: