How to use Color Cop picker to choose colors
Magnify while eyedropping — This option is on by default and allows the user to see a magnified area while eyedropping. The pixel that is being selected will appear in the magnifier window with a black square around it.
Use Cross Hair cursor — The standard windows cross hair cursor can be used in lieu of the eyedropper to select colors.
Relative position measurements — If you press the Control key while eyedropping the coordinates will be set to zero (0,0). When you drag the mouse to a new location the coordinates values will be relative to the point where you pressed control. This is very useful if you want to measure how many pixels a certain object is. Note that if you get a reading of 8,8 the area you just measured is really 9,9 because the zero row and column are included.
Detect WebSafe color — With this option enabled, Color Cop will indicate if the color selected by the eyedropper is WebSafe or not.