Hi Crownedwisdom! Thanks for the complement. <3 I posted before-and-after pics of my latest henna treatment on this thread: Who is using henna currently?
(My curls don't currently hang in front of my face – my stylist suggested I try bangs last January. Never again. So now I'm growing my hair out... Faster, faster I say!
My hair is dark brown too, so you'll notice that henna will leave a translucent red color on your hair, but won't change the color drastically. Like CurlyNikki explains on her website, it's like rubbing a red crayon on black paper: the paper will still look black, but it will be shiny and will have a red sheen in certain lighting conditions. Note that henna may loosen your curls a bit, but getting the moisture balance right usually tames this effect.
Amla is recommended to help curls tighten up. It's an acidic treatment. You can make an amla tea to use as a rinse or you can mix it up into a yogurt-like paste and apply to the hair. When I've used it it's made my curls very springy. It's often recommended to people whose curl pattern has loosened after several henna treatments.