There is a product at Sally's beauty supply called "NO RED"or "RED OUT". I can not remember right off hand. It is a purple liquid you add to your hair dye or can even use when shampooing. I have kept my light brown hair dyed blonde for the last 5-6 years and I have used the red corretor many times. Always had success. Also, try Herbal Essense. I use extra light natural netural blonde and it works great. It has an oil pack you mix in so you hair doesn't dry out so bad.
Dyed My Brunette Hair With Loreal Natural Blonde And Now I'm A Strawberry Blonde, How Do I Get Rid Of The Red And Go Lighter?
It might be best for a hairdresser to do it. You could ruin your hair with the chemicals if you keep doing it and dyeing your hair can strip your hair of it's natural oils and moister.
I'm not a hairdresser, but DEFINITELY don't do anything with ASH! It will turn your hair green!!!
You can't usually go more than one to two shades lighter without bleaching it first and then dying it. Right now I wouldn't do that you could over process the hair and make it really weak and brittle.
Don't try to fix this problem yourself if you want to get rid of this problem,seek a hair expert's advise