Sadhus are Hindu ascetics who follow the path of penance and are in phase number four within the stages of an individual's life established by Hinduism. A sadhu is a monk who follows the spiritual path in order to detach himself from earthly pleasures and materialism. They do this through daily meditation. The saffron-colored robe symbolizes the fact that they have been blessed with the fertile blood of Parvati, Shiva's consort, regarded as the foremost of the Hindu ascetics. You have all the information in: «Indian customs«.
You have all the information in: "Indian customs".