Sorry for the inconvenience. I looked into the script of this object and it does not contain a parameter in the Parameters page of the script to control the pen of that particular element. And as I am not a GDL expert myself I will put this to the attention of the Library Team.
I tried to look at this issue, but when I opened the library part and went to the 2D View, the window was empty except for the Wall and opening. Is there a trick to getting the ArchiCAD Library Doors and Windows to show in this GDL window? This makes looking into these issues more feasible.