Vat Blue 4 is widely used in the textile industry for dyeing cotton, wool, and other natural fibers. It is particularly valued for its ability to produce deep, vibrant shades of blue that are resistant to fading from washing and exposure to light. The dye is applied in a reduced, water-soluble form and then oxidized back to its insoluble state within the fabric, ensuring excellent colorfastness. Additionally, it is used in the production of denim, where it contributes to the classic blue-jean color. Its stability and durability make it a preferred choice for fabrics that require long-lasting color.