Hair dye is a chemical product used to change the color of hair. It comes in various forms, including permanent, semi-permanent, and temporary dyes. The dye works by penetrating the hair shaft and altering its natural pigment, allowing for a wide range of colors, from natural shades to vibrant hues. People use hair dye for various reasons, such as covering gray hair, experimenting with new colors, or expressing personal style. The application process can be done at home or in a salon, and it often involves mixing the dye with a developer to activate the color.