I doubt there's much to be gained by painting a stainless blade (as on the Buck 110), purely for the sake of rust protection. On a carbon steel (non-stainless) blade, maybe so, but only if the paint actually stays put, and if the blade is completely clean beforehand. A bad paint job will likely come off anyway, and might create more problems than it solves (by trapping moisture, dirt, salt and chemicals).
Protecting a stainless blade in a damp environment is usually just a matter of periodically wiping down the blade during the day, and then cleaning it before putting it away. Use Windex or isopropyl alcohol for that. For a little more help, a light coating of mineral oil or WD-40 can't hurt, after the blade is cleaned.
Edit:
As pointed out by Frank (knarfeng) above, I'd be surprised to see or even hear of a 420HC blade rusting. It occurred to me, I don't think I've ever seen a rusted 110, or any other in 420HC. Not to say it can't happen, but it should be extremely rare in this steel.