Good blond highlights can take 10 years off your face and brighten your skin tone. Bad blond highlights do exactly the opposite and more. Highlighting your hair is like any art form: It requires precision, patience, vision and practice. Blond highlights might be the most difficult to do well because such a light color allows mistakes to show easily. However, you can still fix bad highlights in the privacy of your home without spending a lot at a salon or exposing your hair to further damage.
Drench your hair in deep conditioner. Let it sit for at least 30 minutes. Your hair has already been damaged by the bad blond highlights, and you are about to damage it further with more corrective dye. The deep conditioner allows your hair to repair slightly before more stress.
Pat petroleum jelly around the hairline of your face. This is to prevent stray amounts of dye from staining your skin. If the dye does stain the skin of your face or hands, scrub it off vigorously.
Add a dab of blond dye to the bristles of the toothbrush. Grab a section of hair that requires more color, and pat the dye over the lock of hair, from roots to ends, until you saturate it. Fold the lock of hair three times toward the scalp. Wrap the lock of hair in aluminum. Repeat with areas of the hair that require more blond coloring. Leave it on for 20 to 25 minutes and check the tone. Leave it on 5 to 10 minutes longer for lighter highlights. If your hair is naturally dark, you may have to leave the dye on 10 to 20 minutes longer.
Buy a box of dye that matches your own hair color and repeat the process in areas of your hair where there are unwanted blond patches.
Hair dye left on too long can damage your hair significantly. Always have a clock present to monitor how long the dye has been sitting on your scalp.
If your bad blond highlights occurred in a salon, return immediately. True professionals should always be willing to fix their mistakes for free.