Widely used as a blue dye in the textile industry, especially for coloring denim in jeans production. It provides a strong, durable blue color that fades uniquely over time, which is desirable in fashion apparel. Also applied in the food industry as a colorant in some candies, beverages, and cosmetics, where a natural-looking blue shade is needed. Used in histology and microscopy as a staining agent to visualize biological tissues under the microscope. Additionally, it serves as an indicator in analytical chemistry due to its reversible redox properties, changing color based on pH and oxidation state.