Many products claim to cover gray, but you need a special product that is mixed with the color to make the hair "take" the color. Gray hair can be difficult to color because it's so coarse and contains no color itself. Gray Magic is a product that's added to your regular hair color to help the color "take" and can be found at professional beauty-supply stores.
Prepare your hair according to the directions on the hair-color bottle. Many hair-color directions ask you to shampoo and dry your hair thoroughly before applying color. Other hair-color bottles recommend waiting 24 hours after shampoo to color. Make sure you do a "patch test" on yourself every time you color your hair to test for allergies or reactions to the product.
Mix the hair color you've selected according to directions. The hair color is usually permanent or semi-permanent color and is mixed with peroxide. Mix the hair color according to directions only; do not use extra peroxide.
Add the Gray Magic to the hair color and mix well. Use a blend and mix motion; do not "whip" the mixture. Use 10 drops of Gray Magic for every ounce of color. For example, if the hair color you've chosen contains 2 ounces of color, you need to add enough Gray Magic for the 2 ounces of color, or 20 drops. Make sure to read the directions for Gray Magic before you start.
Apply the mixture of hair color and Gray Magic to your hair according to directions and rinse out in the pre-determined time. Unless you are an experienced colorist, it's recommended that a professional apply the hair color and Gray Magic mixture to your hair.