Natural Henna is used in different countries, and the application differs as the cultures vary, let alone that Henna has different purposes of usage.
Natural Henna can be used for hair application as well as body inscription. While there is a common misunderstanding among the majority of Henna users, as they believe that Henna, which is used for application on the hair, cannot be used for inscription on the body, and this misconception results from the fact that most of ready-made Henna products prepared for skin inscription are in fact unnatural Henna or mixed with chemicals that are not suitable for usage on the hair, which is correct, on one hand, but on the other hand this does not mean that natural Henna cannot be used on both skin and hair, See Henna application on hair and Henna application on the skin.
Natural Henna does not actually change the color of the black hair. But it gives it a reddish black shine under the sunlight. When it comes to grey hair, a low quality Henna would have a low Lawsone concentration that can give it an orange color. However, high Lawsone concentration in Henna powder can change the color of the grey hair to reddish brown color when applied properly. If applied on a weekly basis, and after some time, the hair color can become rich brown, leave alone that hair with synthetic dyes is not able to absorb the color of the Henna, but it still can benefit from other characteristics.