Real henna, good henna, never comes in black. You'll see what's billed as "black henna" by unscrupulous henna artists who want to cater to the public's wish for instant gratification, even if it does harm to their customers. Drives me up the wall. Here's why.
Real henna, good henna, is always a greenish-brown paste, made from simply plant powder, essential oils, and lemon juice.
When it's drawn on, it looks like this.
I did this flower on my hand last night.
When the paste flaked off several hours later, the stain looked like this, a cool bright orange.
And today, this is what it looks like. A nice, brown stain that should get a bit darker over the next day or so before it starts to fade... although where it is on my hand, it's likely this one will last close to three weeks!
My only lament? I'm not ambidextrous and can't do another on my right hand!
[Edit: And the day after that]