The resulting colour will depend on your intial hair colour and the method of application and how long it is left on for. It will usually give reddish brown undertones on brown hair. On light coloured hair - grey, white or blonde - it will give a more orange/red tone.
Combining Henna with Indigo to get a red/brown, brown or a black shade
When henna is used with indigo it can give shades of different browns to black. The resulting colour depends on the method used, how long you leave it on for, and the proportion of henna and indigo used.
There are 2 ways of doing this:
Method 1. Dye your hair first with henna so it goes auburn/red then dye your hair with indigo so the auburn/red turns to brown. To achieve the desired shade you need to leave the indigo on for the right amount of time. The longer the indigo is left on for the darker it will be. If you leave it on the maximum time it can go black.
Method 2. Soak the henna overnight. Mix the indigo with water just before you are ready to use it. Thoroughly mix the henna mixture together with the indigo mixture. To get a more red /brown shade use a large percentage of henna. To get a darker brown use a larger proportion of indigo. To get a black shade use Method 1.
Trial and error may be necessary to get the desired shade because everyone’s hair is different and will take the colour differently.
Quantity of henna needed
The following quantities are for average thickness hair:
short hair - 50 gms henna
shoulder length hair - 100 gms henna
mid back length hair - 200gms henna