Getting rid of hair dye

Trish

I have naturally dirty blonde hair that I had a platinum blonde a year ago. After that I had some dye put in brown for a shadow root and blue purple pink etc. the vibrant colors faded but I still have this ring of brown dye that has faded into this brassy brown. I am getting ready to bleach my hair again and I was wondering if anyone had any tips to remove the brown ring? Tia