C.I. Vat Blue 20 (Indigo) is a strategic dye that has defined a global industry (the denim industry). Its core application is to dye cotton yarns into blue with iconic style and color gradation through a unique vat dyeing process, specifically designed for the production of various denim fabrics and products. Its application goes beyond mere coloring; it has become a carrier of cultural symbols and style craftsmanship. Although it is also used in other cotton products, its binding with denim is its core and irreplaceable value.