HELP Dying my hair drastically?!?

So my natural colour is a mousy greyish blonde... Don't get me wrong, I don't actually have grey hair, just dull blonde. Anyway, I have been dying it "black cherry" (which is dark redish) for about 6 months now, with semipermanant dye, and I'm getting really sick of it fading, so I want to dye it dark brown, and I was thinking of loreal casting creme gloss in chocolate brown, but I have heard people say it turns out black!? And how would the brown have an affect on my red hair? Would anything wierd happen? Thankyou! :)