onClipEvent Troubles

(I’m using the MC Tween prototype, though I think my problem is more general and unrelated to the prototype)

Here’s what I have:
An instance of a movie clip (homeMenu_mc).
This mc contains a child mc (home_mc).

On the instance I have this AS:
onClipEvent (load) {
// Sets the first, default _alpha value
this._alpha = 0;

// When the mouse moves over this movieclip, highlight it
this.onRollOver = function() {
// Makes it 100% opaque, on 0.5 seconds
this.alphaTo (100, 0.5);
home_mc.colorTo(0x990000, 0.5);
}

this.onRollOut = function() {
// Makes it transparent again, on 0.5 seconds
this.alphaTo (0, 0.5);
home_mc.colorTo(0x000000, 0.5);
}
}

All the code works execpt the
home_mc.colorTo(0x990000, 0.5); and home_mc.colorTo(0x000000, 0.5);

I can get the colorTo to work but not in when coded like this (referencing a child mc).
So, that’s the problem: how would I reference a child mc in this situation?

I’ve tried:
this.home_mc.colorTo(0x000000, 0.5);
parent.home_mc.colorTo(0x000000, 0.5);
root.home_mc.colorTo(0x000000, 0.5);
etc…

Thanks