Can hair extentions be added onto a different hair color?

Would it look wierd if my hair is black, and I want to add a different color hair color, say brown or highlight blonde? Would it look really fake?Can hair extentions be added onto a different hair color?
Of course it'll look fake, but it's the style. Nobody will know if you had it dyed that way, or if they're extentions. I say ';go for it!!'; The more colors the merrier! :)Can hair extentions be added onto a different hair color?
my friend got different color extentions they didnt Look fake at ALL!