Fairynuff - go back on friday night, saturday morning (or other busy times) and politely but firmly tell them you are not happy with you hair colour, and why. Tell them it is not what you asked for. Do not ask for anything, wait to see what they say, chances are they will immediately offer to fix it, the worst thing for them is for you to stand there with visible evidence of how bad they do things and then behave.
Just before christmas I had my hair cut by the boss and dyed by a new person, the cut was fab, the colour was horrid. I wanted red/orange with blonde highlights, and the hair colour at the base was almost luminous orange and the ends were brown. I felt bad about going back, embarrassed almost but I had spent £80 on it.
When I went back in, I spoke to the person hwy dyed my hair, he looked at it and agreed it was not right. The boss was cutting hair and keeping an eye on things, I could see he realised something was amiss. I did not get grumpy or annoyed, just kept to the facts, reality was, the colour spoke for itself.
We arranged for me to go in the next morning for it to be re-done, and the boss came straight over, apologised, got my coffee, and talked with me and the new guy about how to proceed to make sure I was happy.
They did not at all make me feel like I was wrong for complaining, and I got the impression this guy had got a right bollocking telling off after I had complained!
My hair dressers is an independent one, not a chain. The boss cuts the best hair styles I have had so far.