AJ, they will have a tester kit open in the store so you can swatch colors on your hand and look at the quality. If you like, they can also do your makeup from one of their "clean" testers they keep at the makeup artist station.
And yes, if you do purchase it, try it a few times, and aren't happy with the quality, Sephora will take it back. (I can hear the international readers' jaws dropping right now, but it is true.)