Paint has the best weathering protection. Use the highest number deep tint base---4 or 5----of a good brand name paint.

Test it for yourself, but this paint actually dries clear if nothing---tinting or color----- is added.

You may find some stores will not want to sell this without coloring, and some clerks will say there is no way the base dries clear----but all you need do is say you want a test. Let them prove it to themselves.

Besides, if the color is all they add---that does nothing to change the properties of the paint.

This is a really good idea that I had never heard before. But it makes perfect sense. Clear paint! Why didn't I think of that? Basically, a coat of clear acrylic. There are clear bases and white bases. Be sure you ask for the proper one. The the more vivid colors like red take a clear base. That's part of why they take more coats to cover.

Even the deepest base might dry a bit translucent though. Because you're trying so hard to color match, it's worth buying a quart can and giving it a test on an out of the war spot. HD might sell you one of those little tester bottles full since they use it for mixing samples. Let us know how it turns out.

If it you don't love the look you could put on a couple coats of a satin finish spar varnish. Boring. It's pretty durable for weatherproofing, but where's the manly adventure??? ~;o)

Go to a marine supply and get a clear finish there. It should be a long-oil (spar) varnish. Count on renewing the finish every two years.
Why would a clear paint be any better than a spar varnish? In paints, the manufacturer is counting on the pigment to lend UV protection to the vehicle (oil and resins). Without the pigment, it's no better than varnish. Were it a panacea, the paint manufacturers would be selling it as exterior varnish.
Casey

Most of the folks I know who have used the tint base say the finish is superior to even marine spar varnish.

That is the advice given out on the woodworkers website of which I am a member.

reference for the deep base paint test

Here is a link that might be useful: exterior finishes

Joseph,
I have heard that laminating the wood components pre-assembly with fiberglass cloth and some form of resin (not garden-variety polyester), then an automotive clearcoat, is the way to go for _in extremis_ cases of outdoor horizontal wood. The very thin fiberglass cloth disappears when saturated with resin; the wood grain will still be prominent. Pre-bored holes for fasteners (stainless screws, of course) also have to be treated.
An entry door on a house is not subject to quite as much weather and sun as your benches.
Casey