Early on, they were Haze gray (verticals) and Deck gray horizontals, with either black or red bottoms. The red bottoms faded to a brownish red during the transport over the ocean.
Typically, the came over with 45-48" black-shaded white ID numbers
The offshore elements often retained the gray scheme as it was good agaisnt the horizon.
The inshore and riverine boats quickly gained an overall green. Which green came down to what could be kumshawed by the port and mothership crewes. Hull numbers and ID were paineted over and replaced (mostly) with 12-18" white unshaded numerals. Green color granged from a medium green to an USMC dark green. That later standardized to the same dark green the PBR were in. Some were the same color as Army Hueys.
So, really, your best bet is to pick a reference photo of a particular boat and suss out what matches the references.
Bottoms were either black or red, depending on what the support facility had on hand.
Note, the cabin windows behind the pilothouse were universally replaced with plywood, typically painted to match the hull.
Life rings were a pale gray, not red.
Guns were typically covered under tarps about the same color as the boat.
Swifts were aluminum, so they are not going to show much rust. Gray oxidation, and lots of river slime were pretty common. If they had been used to insert/extract troops, the decks will have red mud in almost all crvices on the main deck.