You also need a recipe. If you put that mud on your skin, let it harden, and then peel it off, you will notice it has left an orange color. The powder gets mixed with water and you get a sort of green-brownish mud.
The leaves of the plant are dried and ground. Henna (or 'Mehndi', the Indian name) is made from the henna plant (Lawsonia Inermis). They painted complicated patterns on their hands and feet to symbolize their fertility. Henna tattoos are an ancient custom in India: girls and women are body painted before ceremonies, like marriage.