Saffron colour is for sacrifice of all those who struggled for the freedom of India, white colour is for peace and green colour is for prosperity.
A freedom fighter once told me that it also stands for the following: saffron for Hindus, Sikhs and Budhists, white for Christians, Jains and Parsis and Green for Muslims. This could be his personal interpretation.
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The saffron colour denotes renunciation, disinterestedness, courage and sacrifice. White colour denotes truth, peace and purity. Green colour symbolizes prosperity, vibrance and life. The Ashok Chakra (wheel) represents the righteousness, progress and perpetuity. The 24 spokes of the wheel represents the 24 hours of a day.