Permanent Dye: They allow for significant hair color change, cover 70%-100% of gray hair, and last for 4-5 weeks, during which time the natural shade begins to show from the scalp.
Temporary Dye: They don't change the hair color, they simply allow for a subtle change in shade, lasting less than 4 weeks.
Henna: Natural plant-based dyes with semi-permanent duration. They do not contain ammonia, peroxide, or synthetic chemicals.