I would probably just have an emf alternate image on the boundary, but here's a version of your script with using different shades of grey for the different arcs.
shape main{
setlinestyle("solid");
SetFillColor(165,165,165);
rectangle(0,0,100,100);
//3 sun auras
SetFillColor(195,195,195);
startpath();
MoveTo(100,0);
LineTo(70,0);
ArcTo(20, -85, 180, 85, 0, 0, 100, 100);
LineTo(100,0);
EndPath();
FillAndStrokePath();
SetFillColor(225,225,225);
startpath();
MoveTo(100,0);
LineTo(70,0);
ArcTo(50, -50, 150, 50, 0, 0, 100, 100);
LineTo(100,0);
EndPath();
FillAndStrokePath();
SetFillColor(255,255,255);
startpath();
MoveTo(100,0);
LineTo(70,0);
ArcTo(70, -30, 130, 30, 0, 0, 100, 100);
LineTo(100,0);
EndPath();
FillAndStrokePath();
// 3 sunbeams
setlinestyle("dot");
moveto(100, 0);
lineto(0, 100);
moveto(100, 0);
lineto(0, 50);
moveto(100, 0);
lineto(50, 100);
}