There are two ways of doing this: The easiest way is to use the eyedropper tool to sample the color as your foreground color – make sure the foreground color square is selected when you use the eyedropper tool – then use a brush, pencil or the paint bucket tool to cover the area. Alternatively, try using the Clone Stamp Tool. Alt+Click where you want to take the color from, and then hold down the mouse key to cover up the new area.