Fashionistas are spoiled for choice in tints, shades and hues, but our rainbow wardrobes come at an environmental cost: synthetic dyes, derived from petrol, are responsible for nearly 20 percent of water pollution by industries. For solutions, we look to the old and the new: rediscovering the woad plant, also known as pastel, whose blue pigment coloured the gowns and shawls of medieval Europe; and visiting PILI's laboratories to meet the team harnessing the power of bacteria in the hope of creating dye on an industrial scale without relying on fossil fuels.