This from John Snyder, of White Ensign Models (Colourcoat has all the colors on his site)
"Flight deck color varied from ship to ship, though generally was AP 507A
Admiralty Dark Grey. Some ships had camouflage-patterned flight decks,
so you would possibly need to be specific about which ship you're
depicting. "
And this from Edgar Brooks on the Aeroscale Forum:
"RN carrier decks were steel; that's why Kamikazes had so much
difficulty; if they came in, at an angle, they just bounced off. As
they were welded, then smoothed and painted, seams would be unlikely.
Normal colour was grey, and tie-downs were rings, about every 6 feet,
with a circular centre, of steel. Apparently you became acutely aware
of them, if you hit one during a game of deck hockey."
And this from Brigandine on the same forum:
"I'm trying to remember the details of this one! Still, it does show a
fairly plain looking deck, with non skid (asphalt based?) surface,
showing tyre marks, and the markings. The elevator in the background has
no distinguishing border painted around it. The whole finish is a dull,
non descript dark grey."
My own particular RN project is of a Bogue Class (Attacker Class) CVE, so it has wooden decks. You'll note that the Just Planes deck would not work at all, either material or tiedowns.
Here's a pic from 1948 of Illustrious. You can see a row of tiedowns under the Seafire.