Look for the Tamiya sets for the M113 APC and "US Command Group" from the M577 types of figure sets... They'll need to have some putty work to "unblouse" the trousers and you'll have to make life jackets on 'em, but they'd be the easiest to convert and all of them have sleeves rolled up... You'll likely need a few heads as well, since what you ask for precludes the Squids from all wearing their steel pots, or you can do some more putty work on the heads that depict stuff like ball-caps, bandanas, or boonie-type headgear, maybe even some dixie-cup hats as well...
I don't know of any sets that are "US Sailors at Rest" types... You'll need to be creative.. 'Corse, come to think of it, if they're not "underway", you could get away with not using the life jackets as well, although there's a few that would have to have the web gear puttied over...
Kinda depends on good you are on Frankensteining, but those Italeri figures would work to supply torsos with vests, combined with the Tamiya figs' legs and lower body and head/arms...
As for the colors of the uniforms, the Sailors would be wearing the standard Navy work dungarees with the light blue shirts/dark blue trousers with the officers wearing khakis...