This reminds me of a great April Fools prank to play on my fellow Mac users: System Preferences > Universal Access > Seeing > Display: use grayscale It's more

This reminds me of a great April Fools prank to play on my fellow Mac users: System Preferences > Universal Access > Seeing > Display: use grayscale It's more subtle than plain inverted colours, and the kind of thing that might make someone think their monitor is dying.