During the movie, when Troy is running down the stairs trying ti avoid Chad, he is wearing a colorful pair of boxers. Then (same day) when he puts his hand up to agree to sing with Gabriella at the auditions, you can see he is wearing white underwear!!
ok obviously they didnt shoot that hole movie in one day so yah of course zac effron is going to change his boxers. i dont think they are gonna care so much that to have the same color boxer every day. and lets all be happy because we know that he atleast changes his boxer. :]