in the map.ini file there is this entry:
HighlightAreasBelowMouse=1
When set to 0 the province under the mouse cursor is no longer highlighted.
Another little step towards simplifying and soothing the look of the map. I appreciate the artistry of the developer in creating the map, and all the bells and whistles, but I just prefer things simpler. Try turning off this highlight - you may like it too.