Continuity mistake: When Hopper climbs to the roof of the convenience store, the time displayed in the upper left corner of the screen (presumably a video surveillance camera) goes from 12:11.57 to 12:12.12, then back to 12:11.34.
Continuity mistake: Towards the end of the movie, when the USS Missouri gets hit by the mother alien ship, the scenes show all of its turrets, or at the very least 6 out of the total 9 turrets getting blown up in to pieces and some of them being snapped, but a few scenes later she is firing back at the alien ship through all 9 of her turrets.
Continuity mistake: When the old guys are getting the battleship ready, there are two on the walk way turning the crank to withdraw the path. When the angle changes to show the walkway moving, the two guys vanish.
Answer: They appear to be versions of a Hawaiian lei. During ceremonies and celebrations, it is permissible to wear pins, ribbons, and other items as a show of respect or support.