I am still working on getting just the right dark shade from henna/indigo for my hair. I have a tremendous amount of white in my hair and my hair very non-porous (hair shaft is thicker to penetrate) so with just henna my white becomes orange which is not flattering to my skin tone. I applied henna and indigo combinations several times on my hair and new white growth but could never achieve a brown of some sort. At that time I did not realize that my hair shaft is extremely non-porous and I would have to leave the paste in for much longer than recommended. I could not go out with orange in my hair so the next day I applied indigo and the results were exactly what I knew they would be - jet black hair.
I rocked the jet black for a minute but I feel it is too harsh and now I'm looking for ways to lighten my hair without chemicals. If you're like me and need to "lighten up" literally check out this fantastic article by a Long Hair Community Discussion Board poster, Ktani. All you need is honey, water and coconut oil!
I will be trying it soon and will report back with before and after pictures.