Nice work on flipping Tetris, and I love the fact that coloured pieces cannot be sent to the player with the same colour. It adds to the chaotic environment in the game.
Just a few nit-picks. Perhaps recolour all sent pieces to white so that the playfield is better seen? And the dropping speed can be faster perhaps? It feels frustrating having to wait for the piece to drop. Lastly, as the T piece actually changes parity of the playfield, maybe intentionally code that T pieces will not be barred from a certain player for, say, 3-4 sets of pieces? I don't know whether it is coded already, but it helps to be player-friendly.
Anyways, super fun game. Good luck!