Eyedropper tool ?

 Eyedropper tool in adobe photoshop

Eyedropper tool used to pick up a color value from the canvas. This is a very useful tool because there will be many time when you want to switch colors while painting to a color on your canvas and you do not want to go all the way through the color chooser dialog. In these cases, simply click on the eyedropper toll in the toolbox and click on the color you want to select inside the canvas. when you do so, you foreground color in your color boxes will change to the selected color.