Hair dyes are products used to change the color of hair. They come in various forms, including permanent, semi-permanent, and temporary dyes. Permanent dyes penetrate the hair shaft and provide long-lasting color, while semi-permanent dyes last for several weeks. Temporary dyes coat the hair and wash out after a few shampoos. Hair dyes can be made from natural or synthetic ingredients. Natural dyes, like henna, are derived from plants, while synthetic dyes are chemically formulated. People use hair dyes for various reasons, including covering gray hair, changing their appearance, or expressing their personal style.