Changing map object colors dynamically via API

HTML

<script type="text/javascript" src="http://www.amcharts.com/lib/3/ammap.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/maps/js/worldLow.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/themes/none.js"></script>
<div id="chartdiv"></div>
<input type="button" value="rotate US color" id="button" onclick="test();" />

CSS

body {
    font-size: 12px;
    font-family: Verdana;
    padding: 10px;
}
#chartdiv {
	width	: 100%;
	height	: 300px;
    float: left;
}
#button {
    font-size: 15px;
    padding: 10px;
    position: absolute;
    top: 50px;
    right: 50px;
}
}

JavaScript

var map = AmCharts.makeChart("chartdiv", {
	"type": "map",
    "theme": "none",
    "pathToImages": "http://www.amcharts.com/lib/3/images/",
	"dataProvider": {
     "map": "worldLow",
		"getAreasFromMap": true
	},
	"areasSettings": {
		"autoZoom": true,
		"selectedColor": "#CC0000"
	}
});

function test() {
    // generate random color
    //var color = Math.floor( Math.random() * 0xffffff );
    
    // update US color in data
    var area = map.getObjectById("US");
    area.color = '#000000';
    area.colorReal = area.color;
    
    // make the chart take in new color
    map.returnInitialColor(area);
}