This would depend on the boat and squadron you are trying to model. As mentioned already the early South Pacific ELCO boats were painted a non-standard green. The actual match for which is a subject of debate. Later pacific boats were painted in a variety of schemes with standard navy browns and greens. English Channel and Mediterranean boats were painted with navy standard blues and greys. Coastal Forces Volume 2is a good reference for paint schemes utilized by specific ELCO squadrons.
As for the paints, White Ensign models had a line of appropriate paints at one time. Now defunct the White Ensign Colour Coat line ceased production. Recently Sovereign Models started producing the line again, but I am not sure which USN colors are available. You will need to check their website.
: Who makes the most authentic colors for USN
: Elco PTs?