To get a brown shade and red highlights or all the shades in between you have to mix indigo and henna together. The more or less indigo or henna used can determine the extent of your hair color.
1 cup indigo
Purified/Filtered water to mix
3 tsp. lavender oil (optional)
Prepare the henna paste. Remember it has to be mixed with a mild acid (orange, lemon etc) and then sit for 12 hours.
Mix indigo with warm water until it has a yogurt -like consistency.
Mix the two pastes together along with the lavender oil.
If you add more indigo than henna, you will get darker brown shades, if you add more henna, you will get redder highlights. You can experiment until you find the right shade to suit your hair.
Part the hair in four sections and apply the paste with your hands (use gloves). Do not be stingy with how you apply the mixture.
Wrap your hair in plastic or use a plastic cap and wrap a towel or around your head to increase the heat to your head.
Leave in for one to six hours, the longer the paste stays in your hair, the richer the color will be. Using an overhead dryer will reduce the coloring time. So if you want rich color in a shorter time, you can use the overhead dryer for a half hour and leave the paste on your head for an hour and a half more.
Rinse the paste out with a moisturizing conditioner. Do not use shampoo. This final step will make the hair feel softer and super manageable. The stain will darken over the next 2 to 3 days.