How to make black mehandi at home to cover grey hair ?

I use a mixture of mehendi powder with tea %26amp; coffee decoction on my hair to colour grey hair. This gives a orange color. What should i do to get black color without using chemicals.How to make black mehandi at home to cover grey hair ?
dont use chemicals,


mix the mehndi for two days in tea and apply it on hairHow to make black mehandi at home to cover grey hair ?
mix powdered mehendi in coffee