This is a henna hair dye method which is much better for your hair health in comparison to a box dye (which has a lot of chemicals that open up the hair shaft and thus dries it out)
It has the staying power of a sort of stain and by that I mean, the more you wash your hair, the faster the colour will fade.
As other people commented, it is a very messy dying method as it is a powder consistency that you mix with a liquid that goes everywhere. But it makes up for it in terms of the price, because it is very cheap . It is about +- R15 from any indian grocery shop such as Gorimas etc.
Used this on numerous occasions. Just make sure you have latex gloves because it doesn't come with plastic/latex gloves. It feeds my hair and adds extra shine. It lasts for quite some time before you have to re-do or touch-up. Very effective.
Leave it on for more than 30mins. Let the product get dry on your hair.
Rinse, rinse, rinse...until the water runs clear. It can be a messy, so make sure you wearing an old t-shirt.