during the underwater fight at the end of the movie, Bond gets his BLUE dive mask ripped off by the central bad guy figure, and replaces the mask with one of the BLACK masks from the bad guys. on the next cut, Bond has the BLUE mask back on, until he exits the water
Not only are the masks different colors, they are also very different shapes! The blue mask has a small round faceplate without a purge valve, while the black mask is larger and goggle shaped with a large purge valve.