Quick question...

[Colosseum]

At some points during the movie, (Master and Commander) you can see some men dressed in uniforms I've never seen before. It's some sort of plain white dress with a beret style blue hat. One of them is seen opening the door for Hollom before Jack gives him the leadership speech, and they're seen while the camera pans back to Jack while the crew is looking at the Galapagos through the spyglasses. Are they Marine sergeants, or some other rank I'm unaware of?

 

[Captain_Python]

Well, drawing from my knowledge, and not remembering the scene in the movie, a sailor commonly had clothes for work and dress clothes. I think it is possible that this dress may have been dress, maybe even the dress outfit of one of the men who man the oars on the ship's boats. Many captains outfitted the crews of the boat that they used all the same in unique styles to make an impression while in ports or in the fleet. There was usually a call to make a good impression when calling on another ship or going to shore for a party. There were some very unique outfits designed by the captains, there being no regulations. That is my guess right now.