Biomes: An all black and white biome would be really cool, the tinting effects all entities, blocks, and the hand (could affect items too possibly). Other colors or even constantly changing colors would be interesting and maybe trippy
Items: An item like a certain type of shaded glasses could change the screen tint and maybe could add some extra effects besides cosmetic
Food: An item like a mushroom or something else could change the colors of the screen temporarily (maybe for 30 seconds to a minute)