Code

var nestedCtrColors = ["white", "gray"];

function outermostContainer(node)
{
	if (node.container)
		return outermostContainer(node.container);

	if (node.children)
		return node;

	return null;
}

function colorNestedContainers(container, level)
{
	container.setBrush(nestedCtrColors[level % nestedCtrColors.length]);
	Array.forEach(container.children, function (child)
	{
		if (child.children)
			colorNestedContainers(child, level + 1);
	});
}

function onContainerChildAdded(sender, args)
{
	var ctr = args.getContainer();
	colorNestedContainers(outermostContainer(ctr), 0);
}

function onContainerChildRemoved(sender, args)
{
	var node = args.getNode();
	if (node.children)
		colorNestedContainers(outermostContainer(node), 0);
} 

Code

Array.forEach(diagram.nodes, function (node)
{
	if (node.children && !node.container)
		colorNestedContainers(node, 0);
});