To select any color from outside of Photoshop first select the Eyedropper tool (I on the keyboard). Then left-click-and-hold inside of your image in Photoshop, and drag the cursor outside of Photoshop to any other window or application. Sample the color that you like, then release your mouse button, and the sampled color will appear as your new Foreground color.
This tip of part of my 5 Photoshop Tricks You Didn’t Know Video.
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