Give you hair a light shampoo to remove any hair products that might get in the way of the color remover. Don't scrub your scalp, though, because that could cause irritation of your scalp once the color remover is applied.
Mix the color remover according to the package directions. Typically, color removers have two separate components that must be combined to activate each other. Gently combine the two ingredients and slip on those latex gloves to protect your hands.
Apply the color remover all over your hair. You really want to choose an oxidative color remover because they target only artificial pigment. That means you don't have to worry about the remover changing your brown hair color, too, unless that was also a dye job.
Let the color remover sit on your hair for the recommended amount of time. When the time is up, rinse your hair thoroughly to remove all traces of both the black hair dye and the color remover.
Follow up with a generous slathering of conditioner to seal your hair's cuticle. At this point you can recolor your hair again, if you really want to.
If you have sensitive skin, or have never used a color remover product before, you may want to do a patch test to check for allergies prior to using this product on your entire head.
Some color removers will remove artificial color and lighten your natural pigment. If you get the one that lifts natural pigment, you'll have to keep a close eye on it and rinse as soon as you get close to your natural hair color.