Here is what you can do, for darker, longer-lasting hair colour, which is safe and has no side-effects. The following preparation will give a natural colour to the hair, instead of the red hair look that henna is associated with.
Change the proportion according to length and thickness of hair. The measures can go up and down a bit, and will not affect the final results. You will need the following ingredients:
1. Henna - 2 cups
2. Amla powder - 1 cup
3. 2-3 eggs - optional
4. Juice of two lemons
5. Hair oil - 2 tbsps
6. Fenugreek seeds (methi dana) - 1 tbsp, soaked and ground
7. Curd - 1 cup
8. 2-3 cloves powder (laung)
9. Iron vessel (not an ingredient, but essential for the process)
Mix the henna and amla powders in very little water, to form a thick, but fluid paste. Transfer into an iron vessel, and allow it to stand for 12 hours. Stir occasionally. This step is essential, as a chemical reaction takes place when the ingredients are soaked in an iron vessel, causing them to darken.
The paste will change its colour, and look blacker. After allowing it to stand for 12 hours, add a little water to the mix, ensuring that it is runny, and heat it, till it starts bubbling.
Allow the mixture to cool. It should be comfortable to the touch. Next, add the rest of the ingredients, and mix well. You can omit the eggs, and add a little more curd, or just plain water. The mix must be reasonably cool when you add the eggs, or else they will get cooked, which we don't want.
Apply the pack to your hair, as you usually do.
The henna and amla powders react with the iron in the vessel, and this chemical reaction changes their colour. Your grey hair will not turn red when you use the henna and amla in this way.
Eggs, lemon, curd and oil, nourish the hair and act as conditioners. Henna can leave your hair dry, so make sure you use eggs, lemon, curd and oil as conditioning agents.
The fenugreek seeds, give a shine to the hair, in addition to changing the cooling property of henna. Cloves also alter the cooling property of henna, making it safe to use overnight and in winter months.
Avoid using henna overnight, especially during colder months. Keep the pack on for 6-7 hours and rinse with water, do not shampoo. Apply some oil, when the hair is still damp and leave it overnight. Wash the hair the next morning.
PS: I studied a six-month beauty course at Shahnaz Hussain Academy.