var targetMc:MovieClip;
targetMc = purple.yellow.blue.green.red;
var pt:Point = new Point(targetMc.x, targetMc.y);
pt = targetMc.parent.localToGlobal(pt);

trace("red global x: "+ pt.x);
trace("red global y: "+ pt.y);

http://www.orlandmedia.com/blog/actionscript-3/localtoglobal-in-as3-not-working/

This demonstrates how to use localToGlobal in AS3.

AS3 LocalToGlobal Example

ActionScript 3