XP, is the paint you used Rustoleum by any chance?

It's a shame you don't have any spare to do some tests on scrap wood. The Minwax poly is an oil based product, and Rustoleum (if that's what you had) is solvent based acrylic enamel (TTBOMK) which is a variant of acrylic lacquer.

I know rabbit is a (or was) a chemist, and maybe I'm just over-cautious/old-school, but I wouldn't put poly over the colour shift without testing first. I personally think it's asking for trouble.