Natural henna brow colour is a form of eyebrow tinting that is used to stain the skin beneath the brow hairs. The purpose of this is to cast a shadow or create an illusion of depth and fullness in the area, visually filling in any sparseness. Henna can last anywhere from 4 days to 3 weeks on the skin. The length of time henna tinting lasts differs from person to person, and is dependent on how your skin reacts to the dye.nnHenna works by coating the hairs, creating the look of thicker hair. Whereas, traditional tint makes the hair darker by breaking down the hair and penetrating colour in the hair follicles. Henna is an excellent option for over-plucked or sparse brows, or for anyone wanting full and even brows, as it temporarily stains the skin underneath the brow.