11 do It Yourself Ways to Fix a Dye Job Gone Wrong ...
6. Green Hair
Use: Red Color Depositing Shampoo, Ketchup
In case your attempt to end your blonde days and join the ranks of brunettes has resulted in a hue that could make any fashion conscious swamp monster go even greener with envy, you will be able to fix it by adding red pigments to your hair to neutralize the green tinge.
Try a color depositing shampoo or mix a bit of temporary dye into your conditioner.
You can try applying ketchup, too, although this DIY hair fix is mostly for blonde hair gone green because of chlorine.