My natural hair is dark brown (almost black looking) and it is dyed dark blackish brown. So I dyed it medium ash blonde and it came out dark brown. So I went to the salon and she did highlight using bleach with a natural medium blonde color and then after used that same color and applied it to my whole head to tone the highlights to that exact color and to lighten the rest of my hair.(not to mention my hair doesn't take dye to well if there is no bleach added) Now my hair is getting lighter as I was it but the highlights are starting to look like an orangy/ reddish (brassy) color. I just want my hair to be a light brown with medium natural blonde highlights. I need some Help

Go back to the salon and ask them to rectify the problem

I agree with ruffwood. Since the salon did the highlighting, return there. She may be able to put a tone or a glaze on it.