The Eyedropper tool makes it easy to copy a color without having to select a swatch. It copies, or samples, the color of an area in your photo to set a new foreground or background color. You can sample from the active image, from another open image, or from your computer’s desktop.
If you want the color always to be available, you can add the sampled color to the Color Swatches panel. You can also specify the size of the area that the Eyedropper tool samples. For example, you can set the eyedropper to sample the average color values of a 5‑by‑5- or 3‑by‑3-pixel area under the pointer.