ColorGroupSwatch sample - InDesign CC 2014 or later

ind_add_color_group_swatch.jsx

//@target "indesign-10"

var doc = app.documents.add();
var color_group = doc.colorGroups.add({name:"CG"});

var ref_swatch = doc.colors.add({
  model: ColorModel.PROCESS,
  space: ColorSpace.CMYK,
  colorValue: [100,50,0,0],
  name: "ref_swatch"}
);

var color_group_swatch = color_group.colorGroupSwatches.add(ref_swatch);

$.writeln([
  color_group_swatch.swatchItemRef.colorValue,
	color_group_swatch.swatchItemRef.name
]);

// => [[100,50,0,0],"ref_swatch"]