KDP Cover Previewer Shows Different Colors Than Your File — What's Actually Happening

You export your cover, open it in the KDP previewer, and something's off. The deep navy looks slightly purple. The vibrant orange looks dull. The whole thing feels a shade duller than what you stared at for six hours in your design software. Before you panic and start re-exporting at random, understand this: you're looking at three separate systems stacked on top of each other, and only one of them tells you anything about what will actually print.