Do you have any photos of the decks from which you could estimate how light or dark the planking was? Mahogany would be too dark almost certainly. White hardwood sounds like Ramin which is the white hardwood used for mouldings you can buy in DiY stores. Lime would be the nearest modelling equivalent colourwise but the wood wouldn’t have stayed that very light shade, apparently it weathers to straw colour so some exterior varnish on the lime would give you a similar effect, just add coats until you get the shade you want.
However, during wartime, some ships had their decks painted but I suppose that would depend on where it was.
Using Ramin for decking sounds a bit surprising to me as it chips and splits easily – maybe it was just a cheap local option for heat insulation in a hot climate?
Colin