Then depending on what shade it comes out at, you can use a box dye to go to light brown (make sure the dye has enough of a lifting agent to get the colour right) 

Hello! Best thing is to pop along to a salon. Grey hair is very course and dry and works differently to ‘normal’ hair, especially when it comes to dye. Oddly, the problem is usually that grey hair won’t hang onto colour. If you’ve tried colour oops I don’t know what to suggest. Did you use the dark one? Did you rinse very well? If so your hair is probably stained, and to get the black out you’d need to bleach, or use a series of box dyes in stages to get back to near your natural colour. You won’t be able to get the colour all out of your hair and back to natural as underneath the dye, your natural colour probably no longer exists as most box dyes have lighteners to make the colour deposit even. Sorry I can’t really help further on this one as any progress from black will be damaging, especially if the removers aren’t working. Please do pop to a salon if you can, they can give you advice for free, then its up to you if you can afford it, or have to let your colour grow out.