Sulfur dyes are a cost-effective class of dyes primarily used for coloring cellulosic fibers such as cotton, linen, and viscose. They are applied by first dissolving the dye under reducing conditions, allowing it to penetrate the fiber, and then fixing it through oxidation to form an insoluble pigment, resulting in durable coloration. These dyes are mainly available in deep shades such as black, blue, brown, and olive green, and are known for their excellent wash and light fastness, as well as low cost. They are widely used in denim, canvas, bed sheets, towels, yarns, and leather.