Pixie is a colour picker that includes a mouse tracker.
Edit by : Pixie is a utility made especially for webmasters and designers. It is a color picker with few extra goodies.

Run it, simply point to a color and it will tell you the Hex, RGB, HTML, CMYK and HSV values of that color. You can then use these values to reproduce the selected color in your favorite programs. Pixie will also show the current coordinates of your mouse pointer.

It is the only tool youll need for working with colors. you can free download Pixie 4.0 now.