What it is: All-natural semi-permanent hair color.What it does: Henna colors by gently coating each strand of the hair. It seals in moisture, giving hair added strength and shine.What else you need to know: Gives 100% grey coverage. Lasts 4-6 weeks. When used on lighter hair, henna will give a more vibrant result. Used on darker hair, it will be more subtle and enhance hair's current color.