Element: instance.fill
Element: instance.fillfillstyle
The fill characteristics for the instance primitive. If this has a value other than no_change, then this overrides the fillstyle for all relevant primitives (glabel, polygon, prism) within the instance.
The value can be a simple color,
a tile pattern, a hatchstyle, a graduation or a composite fillstyle.
Changing this element will redraw the instance.