access symbol in "external" swf AS3

Question

I can do 2-things. Load an external swf, and change the color of an object. When I put these two things together, it doesn't work. How do I change the color of the loaded swf? I want to access instance names in loaded swf files.

WHAT I WAS TOLD
I have to package it and set up a class paths. Is there an easy way for now?

ball.swf

"white ball on the stage named blueball"

load.fla

//load ball.swf
var bgLoader:Loader = new Loader();
bg_mc.addChild(bgLoader);
var bgURL:URLRequest = new URLRequest("ball.swf");
bgLoader.load(bgURL);

//change color of ball to blue "code works in ball.swf" 
var myColor:ColorTransform = blueball.transform.colorTransform; 
myColor.color = 0x066ccf; 
blueball.transform.colorTransform = myColor;

ERROR #1120
access of undefined property

NOTE
swf files are all actionscript-3. I've played with the publishing and security settings.

EXPERIMENT "to understand using symbols in external swf files"

Answer 1

Its because the swf isnt loaded when you try to change the color. You just need to use event and it should work

import flash.events.*;

[...]

var bgLoader:Loader = new Loader();
bgLoader.contentLoaderInfo.addEventListener(Event.COMPLETE, setMyBallColor); 
bg_mc.addChild(bgLoader);
var bgURL:URLRequest = new URLRequest("ball.swf");
bgLoader.load(bgURL);

[...]

function setMyBallColor() {
//change color of ball to blue "code works in ball.swf" 
var myColor:ColorTransform = blueball.transform.colorTransform; // bg_mc.blueball.transform.colorTransform; ?
myColor.color = 0x066ccf; 
blueball.transform.colorTransform = myColor; // same
}

Answer 2

You are missing the "root", after the swf is loaded you can reach the timeline scope using root. Consider the following:

var bgLoader:Loader = new Loader();
bg_mc.addChild(bgLoader);
var bgURL:URLRequest = new URLRequest("ball.swf");
bgLoader.load(bgURL);
bgLoader.contentLoaderInfo.addEventListener(Event.COMPLETE, onLoaded);

function onLoaded(event:Event):void
{
    // use root to reach the timeline scope of the loaded swf
    var loadedBlueball:MovieClip = event.target.content.root.blueball;
    //change color of ball to blue "code works in ball.swf" 
    var myColor:ColorTransform = loadedBlueball.transform.colorTransform; 
    myColor.color = 0x066ccf; 
    loadedBlueball.transform.colorTransform = myColor;

    // just adding the ball to stage, you might want to add all swf
    addChild(loadedBlueball);
}

"In ActionScript 3 the root property refers to the main timeline of the loaded SWF (and not the timeline of the SWF which loaded the other SWF)." *from http://www.adobe.com/devnet/actionscript/cookbook/timeline_root.html*