Artist Takako Saito invented Spice Chess "so that players would be forced to hone non-visual perception" [Claudia Mesch]. All the pieces are identical little bottles filled with different spices, including anise, cinnamon, and nutmeg. Players must remember their positions or use their sense of smell to determine the identity of pieces on the board.
Other versions gave players even fewer visual cues. In weight chess, all the pieces look the same, but have subtly different masses. These works were part of the New York based Flux art movement of the 60s and 70s, which explored games as a vector for art (or vice-versa). Perhaps the most famous Flux chess set was Yoko Ono's white chess. The actual title of the piece is "Chess set for playing as long as you can remember where all your pieces are." All the pieces are white, and the game is played on an all-white board. Often seen as a critique of war, it has spawned numerous interpretations. Some players find it still playable, a taxing but worthwhile alteration. Others have used it to develop entirely new rules for the game.
Imagine if something you believed was inherently adversarial was no longer that way - if the strict black-and-white coloration of the issues was washed out entirely. It would be tough to recall which side you were on, tough to play the game. You might be forced to decide new rules. If only you could agree with your opponent what they are.