Once upon a time I was coloring a clients hair who wanted her hair to be blonde. No problem. I even showed her the color half way through and she said she wanted it to be even more blonde. But then, after we washed her hair she was looking really nervous. I told her to let is settle over the weekend and if she still felt too blonde we could tone it down for her in a week. I was not too surprised when she came in for a tone. It was free because I like to keep my clients happy but while I was toning her hair she said to me "I don't mind paying, I mean, it's not your fault my hair turned out like this." I was a little taken back because, really, who says that!?!?! I was feeling especially snippy and told her - "Of course it's my fault. I did your hair. But you asked to be blonde and that's what I did. It looks really good, you just don't like being blonde." We toned her hair and it looked beautiful. I hope she likes it after all!
But don't say mean things to your hair dresser if you don't want her to "accidentally" mess up, I mean, it can happen.