Oh. I'm pretty sure I know what it is. It's called henna. Henna’s practical use started as a result of the need to lower body temperature in the desert. The henna plant, whose botanical name is Lawsonia inermis has several medicinal properties, one of which is its ability to cool down the body. Upon learning of this effect, the ancient desert people would dip their hands and feet in a mud made from crushed henna leaves. When they scraped off the dried mud they noticed that as long as the colour on their hands and feet remained visible, their body temperatures stayed low.
Besides its practical purposes, tradition in these countries have it that henna is also sometimes used as a lucky charm. It is believed to be able to ward off all kinds of harmful ghosts, black magic, and so on. It is this property of henna that gave birth to an ancient Arab proverb, “If I don’t speak the truth, I won’t present my hand for henna.”
Henna may be used for different purposes depending on the region it is in. For example, in North Africa, an un-named newborn baby about to be named, a young child at the age of seven who can now join in the fasting month, will have their hands dipped in henna. The red palms stained with henna represent his or her entrance into a more important stage of life.
In India, henna painting is an important part of the wedding ritual. It is believed that the deeper the colour on the skin, the longer the love between the married couple will last. In the first month of the marriage, the bride is also not supposed to do any kind of housework. She is supposed to use this time to get to know her in-laws better, and hopefully the henna on her hand would last an entire month, which is considered a very good omen.
Hope that helped. I did a show on henna painting in school a few years back, which is why I got this information.