If you have green hair, there could be a number of causes for the greenish tint, ranging from heavy metal deposits in your ground water, to interaction with previous colors applied to the hair.
It is very common for women to experience a green tint in their dyed hair, caused by chemicals found in chlorine.
Although it can happen to just about anyone who dyes their hair, it is most common among women who dye their hair a shade of blonde.
If your hair has already turned a tint of green due to chlorine, you may want to use baking soda to remove it. Mix baking soda with your shampoo and shampoo and condition as normal.