While I have no knowledge of any existing VFP app like this, I can guess how it should be built.

Mouse events can be traced globally via calling Raw Input API functions or via setting a global hook. The latter requires creating a FLL or ActiveX, the former can be done in just VFP code (VFP9).

Each time MouseDown occurs anywhere on the Windows desktop, the VFP app receives the mouse coordinates and converts them to the handle of a window, then to HDC, then calls GetPixel to obtain the COLORREF.

The following code sample captures keyboard activity on a computer. Same technique can be used to capture mouse activity.

Capturing keyboard activity of another application with the Raw Input API (VFP9)
http://www.news2news.com/vfp/?example=572