I know that I'm not so perfect in designing Mehndi ;but a serious admirer though. Applying Henna has become an integral ritual during Eid , weddings and similar functions back home. As you all know, we indians has got a separate function named mehndi/mailanchi just a day before the wedding. 
I remember when we were kids,we used to roam around to pluck the henna leaves, grind it, then pluck some coconut tree leaves for its thin sticks and then go behind some elders who could apply it on our hands. We try to deepen its color by adding something to it like lemons, black tea, petrol..... ya petrol,, you read it right...
I've seen Arabs mixing some drops of petrol into henna for dark colors. Yes. when we tried it, the color came out deep, but the smell of pure henna was lost somewhere.. Once we dare to add the white ingredient which we use to make Paan to henna; I forgot its name. Actually somebody told us that it was the main ingredient which turns Paan into red while chewing and that would give a nice color to our henna. But what happened was there was no color at all when we washed our hands!! Our palms were blank!!
