This principle is named after a rock band (Van Halen), who had a “brown M&M’s clause” in their contracts with event organizers, stipulating that the organizers must provide M&M’s in the backstage area, but that there must be no brown M&M’s available. This small clause gave the band an easy way to check whether organizers actually paid attention to all the details in the contract, which was important given how complicated and potentially dangerous the band’s production was.
It’s definitely a huge warning.
Kinda the brown m&m test