I don't have a particular Testor's number to recommend. I do have some casual thoughts on the subject.
You're quite right in thinking that different ships used different woods. I suspect that, if the
Yamato and H.M.S.
Hood were anchored side-by-side, the difference in deck colors would be obvious. But plenty of other things influence the color of deck planking: age, maintenance, and even weather. (A wet deck looks a lot darker than a dry one.)
To my notion what's most important is that the color be dull - so dull that the observer doesn't think of it as yellowish, reddish, or brownish, but greyish. To my eye, the typical wood deck is about the color of unpainted pressure-treated lumber, but a little lighter. Color photos obviously are a big help. Black-and-white ones also can be useful. If you know what color the ship's hull was painted, and you can see in a black-and-white photo that the deck was lighter than the hull, that's at least a start. (Beware of the effects of lighting, though. If the sun's shining on the deck and the hull is in shadow, your impression will be distorted.) In most black-and-white pictures of WWII warships that I've seen, the deck planking shows up as having about the same value (i.e., lightness or darkness) as the rest of the ship. With the obvious exception of dazzle camouflage schemes, WWII warships generally look pretty dull in black-and-white pictures.
My favorite deck paint is a PolyScale color, "weathered concrete." I'm sure Testor's makes something similar.
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