Example: You're playing a match against a blue black deck and you're playing green white. If you someone got a swamp and tapped it to produce black there are no ways it can be used as black mana it would need to be used as colorless. Thats the game aspect of it as far as I can understand so I would suppose that as far as the story goes it would be something like that. If theoretically a swamp did exist it would be somehow unable to produce black mana merely colorless as the aspects of black mana would be non-existant on a plane merely of green and white mana.
Example: You're playing a match against a blue black deck and you're playing green white. If you someone got a swamp and tapped it to produce black there are no ways it can be used as black mana it would need to be used as colorless. Thats the game aspect of it as far as I can understand so I would suppose that as far as the story goes it would be something like that. If theoretically a swamp did exist it would be somehow unable to produce black mana merely colorless as the aspects of black mana would be non-existant on a plane merely of green and white mana.