How do you change the colur of dyed hair?

You will first need to use a permanent color remover (such as colorfix) and then bleach to the pale yellow stage and use a toner to get the shade you want.  Expect your hair to be quite damaged doing it yourself, so I would just go to a salon.  Live in the U.S.?  If you're worried about money, Smart Style only charges about $40 or so to do it....everyone will tell you to pay more, but it really just depends on the ability of the colorist.

My hair is dyed black, my natural colur is brown. I want to go to a light blonde, will it go in one go or do i need to get some special stuff or will it not work at all?