Herbatint is able to cover white or grey hair gently and without causing damage to your hair, which enables the chosen colour to last much longer. The natural series colours from 1N to 8N give 100% coverage of grey hair. In order to achieve total grey hair coverage with the Ash, Golden, Copper and Mahogany series of colours, it is suggested you mix the chosen colour ( 40mL ) with a natural ( N ) series of the same number ( 20mL ). For example: Your hair is chestnut and your selected colour is Copper Chestnut. Mix 40mL of Herbatint 4R ( Copper Chestnut ) with 20mL of Herbatint 4N ( chestnut ). Herbatint can be used even if a chemical dye has been used to colour your hair. If your hair has been permed please bear in mind that your hair is more porous than usual, so select one shade lighter than usual for the best results. Herbatint cannot provide 100% colouring power for hennaed hair which still has henna present, as henna creates a coating around the hair. Dry, permed, treated and grey hair tends to be more porous than normal hair and will therefore take up colours more readily. The effect will be a more intensive colour and this should be borne in mind when selecting which colour you require. It is particularly important to leave the products on for the times given. Colours may appear much more intense or even totally different whilst processing takes place. They will not therefore correspond to the colours in the colour chart until the full processing time has elapsed.