I suggest doing an Internet search for "Italian WW2 ships", "Japanese WW2 ships", etc., and then looking at the images found by your search engine. For example,
link
Then there are specialty sites like this:
link
world-war.co.uk/italy/zara.php3
Note that paint schemes changed quite a bit for most navies as the war progressed, so you may have to pick a period. If as you say you want to avoid the complexities of camouflage, then you would presumably use mostly "early war" schemes, which incidentally are those where decks were more likely to still be a natural wood color. For the American "deck blue", if you decide to use it, I would make it lighter than the sides due to fading.
Smaller ships often had a noticeable amount of linoleum-type deck coverings. For example, British DDs early war would have decks mostly in a brown linoleum-like material called corticene. Japanese DDs had a lot of a brown-red linoleum deck covering, also used on larger ships to a lesser degree (see Internet search results above). French DDs and some cruisers often had areas with a wine-red linoleum material, especially the quarterdeck. Like this:
I suggest lightening the colors up a bit, per the concept of "scale color". The rationale for "scale color" is to reflect the lesser intensity of indoor lighting, and to reflect the fact that the farther away something is, the less saturated its color appears to be.
MH
gets started with WWI British in 15mm.
