Apparently Van Halen forbade brown M&Ms on their tours. According to a Rolling Stone blog post, "Buried in the contract was a clause that stipulated there would be a bowl of M&Ms backstage, with all the brown M&Ms removed. They used this to judge how closely the venue had followed the terms of the contract, because if they lapsed in this area the more technical aspects of the production were also suspect."
Van Halen apparently didn't do much M&M chromatography, or they would have known that brown M&Ms are the best!
*see also www.boomeropinion.com