AUROVILLE, India — In the Colours of Nature dye house, Vijayakumar Varathan is busy prepping a vat of indigo. At 51, he looks frail, with a tanned body made mostly of bones, but he runs to and fro, setting up an open fire where he’ll brew cauldrons of natural colorants made from plants.He’s worked here for 15 years. But until his early 30s, Varathan mixed chemicals in a conventional clothing factory in the same region of southern India. There he developed a disease that caused layers of his skin to peel off. Even today, it is discolored. “It was pretty bad,” he says, in his fragmented English. “But I didn’t have a choice.”