It may sound strange, but my haridresser told me once to was my hair a coulple times with dishwasher detergent, then condition in really well. This will strip some of the color out....At the Aveda salon I go to, they did this to me, after I messed my hair and turned it magenta. It removed a lot of it, and then they did hightlights over it to cover it up.
Good luck
joanna