bodycon sexy style items for prom

So after years of henna and being a fiery redhead.. I am starting to consider going back to my natural light-medium brunette color.
I've read the chapter on going back to your root color - in my case I would be going darker to my natural since I lighten before henna - but would the mix with cassia/henna/indigo really cover the vivid copper and red tones in my hair? There are areas of my hair that have multiple applications of henna, it's a big variety of red shades. bodycon sexy style items for prom
I'm just curious if it will really cover the red enough or if it'll still peak through. I'm nervous of going too dark and not being able to lighten the indigo and having a very long growing out process - my hair is down to my hips.