I removed my indigo today by pure accident, while giving myself a citric acid treatment. I have basically liquid stone running from my faucet, and lately didn't have time to play around with distilled water, and I hate ACV rinses. As I am planning to do a henna gloss tomorrow, I decided to get rid of the mineral buildup. I used 1 teaspoon of citric acid in 1 cup of distilled water, warmed it up and poured over my hair, squeezed out the excess, wrapped my head with saran wrap and a towel, and left it on for about an hour. Rinsed out, shampooed and conditioned (to get rid of any gunk, as I use Indian herbs exclusively now, no more shampoo for me!). Something seemed strange when I took off my old T-shirt used for drying: hair was brilliant red with no trace of indigo.
I used Lush Caca twice before, the initial application faded overall, the second one made the indigo stick, while the henna faded a bit. I've applied BAQ henna twice since, but I could still see the indigo lurking from underneath. Now I have cool red hair - I mean RED, lol.