The Michigan Wolverines have their scout team wearing MSU-styled helmets in practice.
When Michigan and Michigan State meet for their rivalry game, both teams take a little time to downplay the importance. You'll consistently find both teams talking about how it's just like any other game, but Michigan is treating it like anything but that at practice. According to MLive.com, the Michigan players on the scout team are wearing green of some kind to emulate their area rivals.
After a bit of digging, we come across this picture on Flickr, which was posted on Uni Watch here. A Michigan player has his helmet taped up with green tape to look like the Spartans helmet. Aside from the fact that it's not a bad mock-up, it seems like a pretty good way to get the players pumped up for what is truly a rivalry game.
As noted in the piece from MLive, it's not the only thing that the Wolverines or Spartans have done to make it clear that this is a rivalry. Michigan has a quote from MSU coach Mark Dantonio in their weight room, in which Dantonio promises wins against Michigan.