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After you have bleached your hair, you need to decide which color you want to have. The cuticle layers of your hair strands have been disrupted in the bleaching process, which allows hydrogen peroxide (a key ingredient in hair bleach) to penetrate the hair strand and strip out color. Depending on your hair's natural color and how long you left in the bleach, your hair now might be yellow, white or reddish. Food coloring typically comes in four colors (red, yellow, green and blue), each of which can be mixed with another to achieve a spectrum of color choices. Red and green make brown, for example, while yellow and red make orange, and blue and red make purple. Take into consideration the color of your bleached hair. This will act as an additional color in your overall color mixture. Mix drops of food coloring with shampoo in an empty shampoo bottle. Add 6 drops of coloring to every ounce of shampoo. Mix up enough shampoo to cover the amount of hair you want to color. Tightly seal the bottle and shake until the contents are completely mixed. Add 1 tablespoon of water and reseal the bottle. Shake for another 2 minutes. Your color is now ready to use. Gather up a small hunk of hair from the nape of your neck. Brush the dye onto this strand, starting at the roots and working it towards the ends. Set your timer for 20 minutes and check the color. Add more time if it seems like the color is not quite where you'd like it to be. Rinse out or wipe off the dye and check the color against a white towel. This will enable you to check if you like the color before dousing your entire head in it. It will also help you gauge how much time to leave on the dye. Divide your hair into four sections. Pin back three of these sections while you apply color to the fourth section. Work the dye into your hair, starting at the roots and working towards the ends with your hands. When you've applied to all four sections, rub the dye all over your hair as though you were shampooing your hair. Cover your hair with an old shower cap and leave this dye on your hair for anywhere from 30 minutes to 3 hours, depending on how dark you'd like it to be. Start your timer when you have put color in the last section of hair. Gently rinse your hair with warm water to rinse out the leftover dye. Rinse until the water runs clear. Use a towel or blow dryer to dry your hair. Alternatively, you can let it dry naturally. Because you haven't used chemical-based color to dye your hair, your hair won't be as dry and brittle and can therefore handle blow drying immediately after dyeing it. Water, soap and heat can lessen the dye's hold on your hair and cause it to escape. Leaving your hair alone for three days will enable the dye to sink into the cuticles of your hair. You may experience an unwanted color in your hair after the color fades. For example, if you bleach your hair and then dye it bright red, you might get orange hair after the red fades.
Determine what color you want to dye your hair. Mix up your color. Do a strand test. Apply the dye to your hair. Cover your hair and start your timer. Rinse your hair. Dry your hair. Avoid washing your hair for 2-3 days.