Vat dyes are water-insoluble dyes used in cellulosic fibers and are based on the chemical structure of indigo and anthraquinone. Through the dyeing process, the dye becomes soluble through reduction. After the dye is absorbed by the fiber, it becomes insoluble again through an oxidation reaction. Vat dyes have high light fastness and washing fastness, and moderate rubbing fastness, so they are suitable for jeans.