I wanted to test something with different colors, turns out it’s easy to pick a random color:

var box:Shape = new Shape();
var random_color:Number = Math.random() * 0xffffff;
box.graphics.beginFill(random_color, 1);
box.graphics.drawRect(0, 0, 100, 100);
box.graphics.endFill();
this.addChild(box);