I understand.
Don't ask Home Depot, that will get you a flat no.
I have used Minwax, Spar Varnish - same as you are talking about.
I did use a Minwax stain thinking it would mix well, but it really just was suspended in the varnish and never got to be a smooth color. You won't find the colors you want anyway from Minwax.
What you might notice was that this one part polyurethane will get darker when it completely penetrates the skin and touches the frame. There is a spot near the bow on the gunwale in the picture. I have never been able to avoid some of that blotchy-ness.