The festival of colours (Holî or Phâlgunotsava) is Hindu festival of the vernal equinox. It celebrates the fertility and also it represents the rite of Spring. It can be seen anywhere in India, for two days during the full moon of Phalguna month, between February and March. The Holî is in honour of the godhead 'Krishna' in the northern India and Kâma in the south.
The first night of the feast, a fire is lit, it symbolizes the burning of Holika. The second day, people dressed in white, set off colours on each other, followed by "Bura na mano, Holî hai" ('Don't be angry, it's Holî'). This is also the opportunity to eat special food for days of Holî.
Of course, the colours have a specific meaning : green for harmony, orange for optimism, blue for the vitality and red for joy and love. In the evening, when the calm reigns, the people visit their family and friends. The festival of colours has virtues, it's also symbolic, during few days the social barriers fall, men and women are equal.
Holî has a powerful unifying spirit, Spring is the time to forgive his enemies and to show his love to his family and friends. Holî also has medicinal virtues, colours penetrate the pores which enhances the natural defences of body and embellishes it.
Wikipedia on Holî