How can I draw an object of a specified color over objects of varying colors
  and then erase it without having to redraw everything else?

  What's happening is this,

      If I draw it using GXcopy, it is drawn in the specified color.  If I erase
      it using GXcopy with foreground and background reversed, it erases 
      whatever it overlayed.  I then need to redraw
      all of the items it crossed.  Yuch.

      If I draw it using GXinvert it is drawn in a random color - nothing 
      resembling what I requested.  It properly restores the color of 
      underlying objects in erase mode.

  What's the solution?
     
