There's no simple answer to this question, because the color schemes of wood ships have varied so much over the years - and from country to country.
The Ronnberg article that Ed mentioned is excellent, but it really concentrates on American ships of the nineteenth century. The subject goes considerably beyond that.
Getting back to the Wasa for a minute - recent research has established pretty firmly that our earlier concept of what she looked like was wrong in many ways. Study of the surviving paint work (and other treatments applied to the wood) suggests pretty firmly that her hull, below the level of the carved decorations, was coated with a layer of tar, as a preservative. There is no evidence of any different treatment below the waterline. The background color behind the carved decorations seems to have been a rich red, and the carvings themselves apparently, for the most part, were painted in "natural" colors, rather than gilded as had previously been assumed. So an accurate model of this particular ship would have a quite dark brown hull, with red upperworks and intricately painted carvings. Quite a project on the scale of the Airfix kit (which, by the way, is an excellent one).
The color of an unpainted wood hull can vary tremendously - depending on what kind of wood it's made of, how old it is, and what sort of preservative (if any) has been applied to it. Those preservatives ranged from tar (dark brown) to various forms of oil (brownish-yellow when freshly applied, but darkening as it got older). The Wasa is kind of unusual in that her underwater hull apparently was the same color as the above-water part. During most periods some different substance was usually applied to the hull below the waterline, in the hope of discouraging marine growth and worms. The colors seem to have ranged from off-white to near-black. (The former is much more frequently seen in models.) In the middle of the eighteenth century navies began experimenting with metal sheathing - usually copper or some variation of it. Copper sheathing was in common use by 1800. How to represent it on a model - well, that's another subject.
In other words, there's plenty of room for personal taste on the part of the ship modeler. My suggestion is to look through some books and websites for contemporary pictures of ships from the period of the one you're modeling. See how the great marine artists depicted their ships' hulls, and work out in your head an impression of how you'd like yours to look. (Sailing ship modeling probably gives more room for "artistic license" and personal taste than any other form of scale modeling.) Then see what the paint manufacturers have to offer - and if they don't make the color you really want, don't hesitate to mix your own.
A couple of companies used to make ranges of premixed colors that were designed specifically for ships models, but most of them have been discontinued. To my knowledge, the only ones currently being sold are the few "ship colors" in the Humbrol range and the line of acrylics from Model Shipways: http://www.modelexpo-online.com/search.asp?SKW=cat1_gp cat2_p0 . I've had pretty good luck with those paints, and I like the color selection. I have no idea, though, how hard those paints may be to get in Europe.
Hope that helps at least a little. Good luck.