You need to create an instance of GPolygon and add it (using addOverlay ) to the GMap2 object:
var polygon = new GPolygon([new GLatLng(48.922499263758255,-94.921875), new GLatLng(49.03786794532641,-128.671875), new GLatLng(38.95940879245423,-126.38671875), new GLatLng(31.95216223802497,-118.30078125), new GLatLng(24.686952411999155,-96.50390625), new GLatLng(28.149503211544566,-87.1875), new GLatLng(23.725011735951796,-79.62890625), new GLatLng(44.59046718130883,-59.765625)], "#ff0000", 5, 1, "#0000ff", 0.2); map.addOverlay (polygon);
The first parameter is an array of points (which make up your polygon), then the stroke color (this is the outline), weight (thickness) and transparency (like transparent), then the fill color and opacity.
The following is an example:
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