Deck blue - Navy shade 20-B. I don't know if Model Master makes it. Colour Coats do. Dark Sea Blue lightened a little bit would be close. They used stain, not paint on the wooden flight deck of US carriers so the color isn't uniform. It looked a little streaky I believe. Actually, I see that Colourcoats makes a color (or should I say, "colour" ;-)) called: "Flight deck stain 21" that is probably exactly what you need. It's available from the site below or from other sources.
This site: http://www.shipcamouflage.com/ will tell you everything you want to know.