Before colouring your hair, be aware that grey hair does not hold colour like other hair types. It has a different type of texture and does not contain the pigments found in non-grey hair. If not done properly, your grey hair may not absorb the colour or the colour may fade out after shampooing only a few times. To avoid this, your hair stylist can add a solution of peroxide to your hair before colouring. After the peroxide has been on your hair for a short time, the grey hair should be able to hold colour better.Another option is to have your hair highlighted. Highlights will help the grey hairs to blend in better and presents a more natural look. Highlighting techniques generally work better on people who have blond or light to medium brown hair. If you have dark brown or black hair, you know what a contrast there is between your natural and grey coloured hair. People with dark hair may opt to keep their hair trimmed shorter to minimise the effects of the grey colour or they may choose to change their hair colour completely to a lighter shade.
Source. http://www.mid-day.com/web/guest/specials/zing/article?_EXT_5_articleId=886741&_EXT_5_groupId=14
