There were two types- some Navy Auxiliaries (AK, AP) or Army Transports (AT), and a whole lot of United States Maritime Commission ones (SS).
Putting aside that its possible to find a photo of just about anything, the USMC ones were overall one color of gray. I've seen the overheads white and the interior decks red, but otherwise all one color of gray. Because they were built in commercial shipyards, the paint spec. was not a Navy Measure. 5-O Ocean Gray is considered a close match.
The only exceptions would be the stack top (black) and the tarps over the hatch covers.
There was no bootstripe during the war.
Crewmember, SS Jeremiah O’Brien
Ignore the Trumpeter directions.