Early in the war U.S. fleetboats were all black. Around the middle of 1944, the Navy changed to a paint scheme that was a light gray overall with black on the upper, horizontal surfaces...and there were two variations of that scheme.
Here's what the USS Ling
looked like back in July 1945 (click on the thumbnails for larger views):
The paint scheme diagram for this would be:
-hope this helps,