Has it ever happened that when you want to use the Eyedropper Tool in Photoshop to grab a color, it goes to the background color instead of the foreground? It just happened to me. Sure, it’s easy to switch front to back colors by pressing X, but it won’t stick.
So, to make the test permanent, go to your Color panel by pressing F6, and choose the foreground color. You will see a light glow on the foreground color rather than the background… and you are all set!