Changing Objects with Actionscript?

I have been playing about with the “Changing colors with Actionscript” FLA found on this site.

Basically, when you move your mouse over a coloured box the movie clip changes to the corresponding color.

This is the AS

on (rollOver) {
var colorful = new Color("_root.shapes");
colorful.setRGB(0x003366);
}

I am trying to change the AS so instead of changing color, the movie clip changes an image?

Can someone please help me?