Is Indigo permanent on hair?

So, I’m a natural brunette and I’ ve been using henna for 3 months. I really like the orange:reddish shade of my hair now but I wanna try something new and use indigo to obtain jet black hair. If I don’t like it or simply I wanna change again after a while, can I return to my brunette reddish hair? Indigo will simply fade If I don’t keep doing it?