Turning my comments into this answer.

If they're real hardwood (typically 3/4" thick), they should be able to be sanded down to remove all or most of the offending stain. Then re-stained to whatever color you want. This is probably a job for a professional.

If you decide to do this as a DIY project, I would caution you against using a big drum sander (what you would need for a job this big) yourself, unless you've handled one of these things before. They can get away from you in a heartbeat. Let it sit in one place for more than a second or so and you now have a big rounded gouge in your floor. Even if you don't let it sit, just changing the pace at which you move the sander along the floor can leave some uneveness. Been there, done that!

If they're real hardwood (typically 3/4" thick), they should be able to be sanded down to remove all or most of the offending stain. Then re-stained to whatever color you want. This is probably a job for a professional.

If you decide to do this as a DIY project, I would caution you against using a big drum sander (what you would need for a job this big) yourself, unless you've handled one of these things before. They can get away from you in a heartbeat. Let it sit in one place for more than a second or so and you now have a big rounded gouge in your floor. Even if you don't let it sit, just changing the pace at which you move the sander along the floor can leave some uneveness. Been there, done that!