Permanent dye is a type of hair color that provides long-lasting results. It works by penetrating the hair shaft and chemically altering the hair's natural pigment. This process allows for vibrant colors that can withstand washing and fading over time. Unlike temporary or semi-permanent dyes, which wash out after a few shampoos, permanent dye typically requires a more complex application process. It often contains ammonia and developers, which help open the hair cuticle for better color absorption. Many people choose permanent dye for its durability and ability to cover gray hair effectively.