I don't know of any product that can give you what you want in one
coat, but I recently have been using Kleer Kote, a 2 part epoxy. I
bought it in gallon jugs (1 epoxy, 1 hardner) plus pumps that would
push out equal, small amounts. see
http://www.shopmaninc.com/pdf/kkote.pdf for more info. I don't recall
who I bought it from except it was a company in Florida. It cost me
about $45 delivered I think.
This is one product where you want to read the instructions thoroughly
& do exactly what they say. The pdf I point to above is 3 pages & all
you need to know, except that you really want it at least 70 degrees to
use it. I coat bowls with it, generally after turning them green &
drying them in a microwave. Thin coats! I buy those cheap plastic
clear cups & mix it up in them, apply with a foam brush. Works great!
I'm not sure how well it works for exterior projects, but I did put 2
coats on the top of an old picnic table that sits on my open porch last
summer. So far, so good. We've had temps down to about 10 degrees &
other days up to 90, so far. It hasn't cracked yet, but it's been less
than a year.
It doesn't really change the color of your project - but changes the
contrast - kind of hard to explain. You know how polyurethane will
soak in & make the contrasts in the grain more apparent? This does the
same thing, but even more so. It REALLY soaks in. I've used it on
rotted wood & it can take several light coats before it stops soaking
in & builds up. I made a Willow bowl (very porous, close to rotting)
which weighed nothing & now it weighs a pound.
I think this will do what you want, but I'm not sure that the soaking
in of the product won't be a problem.