We just had six lovely alder wood gates made. In order to make them look more like golden oak, the carpenter stained them a yellow color and then finished them with 4 coats of Minwax Helmsman water based indor/outdoor Spar Urethane. Unfortunately, the yellow we chose looks terrible with our remodeled exterior. We needed something that was more caramel colored and I think I can get there with a top coat of stained urethane. Can I add Mixol to the Helmsman Spar Urethane? Then how do I apply it? Lightly sand and simply apply like a final coat of urethane? Will it last? Thank you for your help.