Covering red hair dye with a darker hair color is extremely easy. In fact, the easiest hair-color jobs are ones that deposit color to correct or cover an existing dye job. The most important factor in covering red hair dye is color selection. Previously colored hair has a tendency to grab or soak up color. So if you choose a color that's exactly what you want, you may be disappointed when your hair turns out a shade or two darker. To prevent this, choose a color that's one shade lighter than your desired shade.
Start by pouring equal parts hair color and developer into the color bottle. Close the lid and shake the bottle until the color is completely blended with the developer.
Part your hair down the middle. Create a second, horizontal part from ear to ear and across the top of your head. Your hair should now be separated into four sections. Pin the sections with hair clips. To protect your clothes and skin, place a towel over your shoulders and put on latex gloves.
Remove the hair clip from one section. Apply hair color from root to tip using 1/2-inch cross sections. Continue applying color until the entire section is saturated. Move onto the next section and repeat the process. Continue until all hair is thoroughly saturated with color.
Wait 20 minutes. During this time, take off the latex gloves and clean up any mess from the dye.
Rinse out the color with lukewarm water until the water runs clear. Shampoo your hair and follow up with a conditioner. Rinse out the conditioner, towel dry and style as desired.
Color selection is vital. Avoid colors that contain a red base, which are typically described with words such as warm, chestnut and mahogany. Ash colors contain a green base that neutralizes red. Words to look for include cool and ash. Always use cool, ash colors to cover red hair color if you don't want to see any red tones peeking through.
Hair color starts to oxidize as soon as it's mixed. As hair color is oxidizing, it continuously gets darker. A medium-brown color may oxidize to the point that it appears black, but it's no cause for concern. Your hair won't turn black as a result of oxidation.
Rub a thin layer of Vaseline around your hairline to prevent the color from staining your skin. If a stain occurs, it will fade within a day or two. If the stain is in a conspicuous location, color remover will remove the stain. You can purchase color remover at any beauty supply retailer.