I used to work in a roadhouse, and I remember one band had this in their rider as a joke… But our producer actually took the time to pick out all of the brown ones from a giant fishbowl.
The band was equally amused and horrified when they realized. The lead singer was like “yeah we added that to our rider as a joke. We’ve never had anyone actually do it before. Now I feel kinda bad that she had to sit there and dig all of them out…”
Meanwhile, she had an entire bowl of brown M&Ms sitting on her desk to snack on.