I found it myself :
It was in : View >> background, had to be changed to solid, and color to white
now I need to change the color of the coordinate system text from white to black
If you posted this in one of the "simcenter" forums (e.g. "3D sim - FEMAP") , you might get better response.
This forum may not be monitored by most FEMAP users
Production: NX10.0.3.5 MP5 + patch/TC11.2
Apparently I've turned into a gearhead