Bill's right: if you look at the deck of a real ship and remove any prediliction you may have to think of it as "brown" or "tan," you'll conclude that it's essentially grey - maybe with a faint brown or tan tint. Teak, in particular, starts turning grey pretty quickly when it's exposed to the atmosphere; left to itself it will eventually look almost silvery. (But ships' decks weren't left to themselves, of course.)
I have to say I have mixed views about the Model Expo/Model Shipways paint line. I really like the range of colors; the people responsible for formulating them knew what they were doing, and put a good deal of effort and research into the project. There's no way that sailing ship colors can be determined as precisely as those of modern warships and aircraft, but these are about the best guesses possible. Some years ago I ordered a big assortment of them. Some (the blacks, whites, reds, yellows, and browns) worked beautifully; in fact I'm still using the same jars. Others (most prominently the blues and greens) I just can't get along with. They have a syruppy, oily consistency that resists all efforts to brush it, and dry translucent. It's possible that the age of the jars I've got is a factor, or that I got a bad batch. But I've heard similar complaints from other modelers.
In any case, the Model Shipways range, though it includes several nice shades of brown, doesn't include any that are identified as matching wood species (teak, oak, etc.). The company does sell some wood stains, which, I'm fairly certain, are just Minwax stains (the ones you can buy at Lowe's or a hardware store) in miniature jars. That's not necessarily a criticism; Minwax products are excellent. But such stains have limited use for the plastic modeler. I certainly wouldn't recommend them on bare styrene.
The Testor's Acryl "Marine Colors" were only on the market for a little while a few years ago, and, unfortunately, have been discontinued. That's a real shame. I was lucky enough to grab quite a few of them at a hobby shop when I had the chance, and I find them extremely useful. (I think they were formulated to match the old Floquil lacquer "Marine Colors." Floquil, Pactra, and Polly-Scale - that is to say, virtually all the well-known American hobby paint brands - are now owned by Testor's. That's kind of scary.)
In the realm of hobby paints - as in so many others - the sailing ship modeler is usually either ignored by the manufacturers or treated as a poor relation. But don't despair. A great deal of "cross-pollenation" is possible in the world of hobby supplies if you know where to look.
My own personal favorite brand of hobby paint is Polly-Scale acrylic. (Actually I liked its predecessor, Polly-S, even better - but Polly-S is long gone.) The Polly-Scale line of railroad colors includes a lot that are appropriate for ship models. Ignore the cryptic designations like "Santa Fe," "Great Northern," and "DRGW," and you'll find some mighty nice yellow ochres, greens, browns, reds, etc. And the one they call "Aged Concrete," to my eye, makes an excellent start for a realistic deck color: http://www.testors.com/category/137367/Railroad_Acrylics
If you're lucky enough to have a genuine hobby shop within driving distance (I wonder how many of us are; I feel like I'm fortunate that there's one 35 miles away), take a careful look at its paint department. The manufacturers nowadays are catering extensively to aircraft, railroad, automobile, and armor modelers. The car paints, most of which are high gloss, aren't likely to offer the ship modeler much (except some interesting metallics), but all the others do. The camouflage ranges used by armies and air forces contain an endless variety of greens (not so common on ship models) and browns (very useful). Again - the fact that it's intended to be used on WWII Italian aircraft is irrelevant; what matters is what it looks like. Testor's also has a small range of acryllic colors designed for figure painters. That batch includes shades like raw umber, burnt sienna, and some flesh tones that offer all sorts of possibilities for the ship modeler.
A few months ago my wife got involved in a hobby that involved acrylic paints, and sent me to the paint department of the local arts and crafts shop. (We have one of those - Michael's - here in town.) That was a moment of revelation. There are several companies (which I'd never heard of previously) that make enormous ranges of acrylic paints for use on wood, ceramics, and heaven knows what else. One brand is called "Apple Barrel": http://www.michaels.com/art/online/displayProductPage?productNum=cp0225 ; there are others. In combination, those ranges number in the hundreds of colors. Dozens of reds, dozens of yellows (there's a perfect match for the stripes on Nelson's warships in there somewhere), dozens of browns, buffs - you name it.
They're packaged in nice, neat squeeze bottles - and on a per-ounce basis they cost less than a tenth as much as Testor's or Polly-Scale. (The day I showed up at Michael's looking for paint for my wife, the Apple Barrel range was on sale: 50 cents for a two-ounce bottle. That compares to $3.30 at Squadron Mail Order for half an ounce of Testor's Acry. In these trying economic times....) Their brushing consistency is, to my taste at least, excellent, they cover just as well as the usual hobby brands, and they dry about as fast. I'm not sufficiently versed in chemistry or physics to comment on how long these things will last, but my wife and I have used quite a few of them over the past seven months or so and so far they look fine.
One big factor that keeps me from becoming a complete convert to "craft acyrlics," though, is my stubborn loyalty to the local hobby shop (the one 35 miles away). When I was in college I had a part-time job in a small hobby shop in Ohio. The boss's method of operation was, I think, fairly typical of small hobby shops (at least in those days): he bought all the merchandise on credit, with the bills coming due at the end of January. When the Christmas rush (train sets, radio-control airplanes, HECEPOB ship kits, etc.) was over, he'd sit down to do the books and find out whether he'd gone bankrupt or not. (Several of his local competitors did precisely that.) I'm sure the business has changed in various ways (not all of them for the better) since then. But as I read the news reports about how disappointing this holiday season has been for merchants of various sorts, I find myself wondering how many more American hobby shops are going to disappear within the next month or so.
Anyway - I think it's safe to assume we'll always have good paints available. But it's not a bad idea to think a bit flexibly and creatively about where to get them.