Colour B4 does not make your hair ginger. That is the actual colour of most people's hair after they have dyed it and it is caused by hairdye.
So yes, if you use Colour B4, your hair will likely be ginger. But your hair is already ginger right now, all colour B4 does is let you see the ginger that's already there.
Anyway, this product works really really well.
I had Schwartzkopf Live XXL Midnight Blue (which was blackish) and Colour B4 (the strongest type) got my hair back to a lovely copper colour in one application. It got all the black out, I was actually amazed by how effective it was.
It will fail to work however if you've used a lot of heat on your hair, straighteners in particular. This is because Live XXL contains silicone. Heat melts the silicone and then when it re-solidifies it effectively encases your hair in an impenetrable silicone force-field. Even bleach couldn't do much about it, so don't go blaming the Colour B4 if this is the case.
Some people say Colour B4 doesn't work but they're almost invariably people who either failed to use it properly or to do adequate research into whether it would work on their hair.