Word to the wise

I have been successfully dyeing my hair for 17 years. Today I broke that run of success. My hair is green. I was trying to go from blonde with brown roots to brown and ended up with green-gray. I went to the beauty supply store and bought what the nice cosmetologist
told me to. I used said product and my hair is still slightly green. I thought your hair only did crazy color things if you were trying to lighten it more than a few shades. Apparently trying to return my hair to it's natural color will result in a color more appropriate Halloween than everyday. I guess it's a sign that I really should stick with blonde because it fits me so well.