I know it varies depending on the 'theme' night. You'll definitely need to buy the daytime shirt onboard. Formal nights are the standard tux shirt (don't remember pleat or plain)/ tux jacket/bow tie. I work in another division, and I seem to remember some of the guys wearing dark suits. It really depends on how strict the ship and hotel director are on the look.
I don't remember if the daytime pants are blue or black, but I can find out everything for you soon