Van Halen and Brown M&Ms
According to David Lee Roth, this was listed in the technical portion of the contract not because the band wanted to make capricious demands of the venue, but rather as a test of whether the venue had actually read and honored the terms of the contract, as it contained other requirements involving legitimate safety concerns.
The band developed the M&M's demand as a means of checking whether the venue was properly honoring the terms of the contract to their satisfaction. Subsequently, if the bowl was missing, or if there were brown M&M's present, they had reason to suspect that the venue might not have honored legitimate technical and safety concerns within the contract. As a result, the band would be within their rights to inspect the technical side of the performance prior to going on stage, and/or request the venue redo their work properly.