I think I found an infinite black mana combo in only black, though it is quite complicated. Soldevi Adnate turned into an artifact with Ashnod's Transmogrant.
Arcbound Worker Dross Scorpion Rattleblaze Scarecrow all on the battlefield and Disturbed Burial in hand. You sac the Rattleblaze Scarecrow to the Soldevi Adnate to get 6 black mana, also causing the Soldevi Adnate to untap because of Dross Scorpion. You also sac the Archbound Worker to the Soldevi Adnate to get one more black mana, untaping it and getting a +1 +1 Counter on the Rattlebalze Scarecrow. You finally cast Disturbed Burial with buyback to get Arcbound worker back for 5 mana, then cast Arcbound worker for 1, netting you 1 black mana. All commons and all the more complicated.
Arcbound Worker Dross Scorpion Rattleblaze Scarecrow all on the battlefield and Disturbed Burial in hand. You sac the Rattleblaze Scarecrow to the Soldevi Adnate to get 6 black mana, also causing the Soldevi Adnate to untap because of Dross Scorpion. You also sac the Archbound Worker to the Soldevi Adnate to get one more black mana, untaping it and getting a +1 +1 Counter on the Rattlebalze Scarecrow. You finally cast Disturbed Burial with buyback to get Arcbound worker back for 5 mana, then cast Arcbound worker for 1, netting you 1 black mana. All commons and all the more complicated.