Overuse of Coloring Agent

A: Well, with any color correction, you have to select a color to neutralize the unwanted tones.
Visit your local beauty supply shop and look for a hair color formula that is approximately the same shade as your current color, or a little lighter, but has an orange base color. You'll want to combine it with equal parts of 10-volume peroxide developer.
Use half the color (one ounce) and one ounce of the developer, and combine these with an ounce of your favorite conditioner. Apply this all over the hair, starting with the areas where the hair is blue from the drabber.
Allow this to process for 15 minutes then rinse the hair and shampoo to remove the color mixture. Dry the hair fully and examine the results. If you need it, you can make a second application. If not, the remainder can be saved for future needs. Store the unused portions in a cool, dark, dry place.
©Hairfinder.com
See also:
Hair coloring
The hair color wheel