There are some dye-removal products like "Color Oops" out there. They might help you, though depending on what you used to dye your hair, you might have some weird colors going on beneath the dye. (Lots of dyes, even black ones for reasons I don't comprehend, contain peroxide. So your hair might be lighter after removing the dye than the hair that grows from your follicles.)
A lot of these have a bottle with some sort of peroxide in it, as a final step I think. I've been told you can completely skip that step. It may take a few days to a week for your hair to reach whatever final shade it's going to be if you skip that, but I think avoiding the damage makes a week of oxidation worth it.
In any case, strand test!