amcharts Column chart with multiple datasets

HTML

<script src="http://www.amcharts.com/lib/amcharts.js" type="text/javascript"></script>
<div id="chartdiv" style="width: 100%; height: 362px;"></div>

JavaScript

var chart;
            var chartData = [];
            var chartCursor;

            AmCharts.ready(function () {
                // generate some data first
                generateChartData();

                // SERIAL CHART    
                chart = new AmCharts.AmSerialChart();
                chart.pathToImages = "http://www.amcharts.com/lib/images/";
                chart.zoomOutButton = {
                    backgroundColor: '#000000',
                    backgroundAlpha: 0.15
                };
                chart.dataProvider = chartData;
                chart.categoryField = "date";
                chart.balloon.bulletSize = 5;

                // listen for "dataUpdated" event (fired when chart is rendered) and call zoomChart method when it happens
                chart.addListener("dataUpdated", zoomChart);

                // AXES
                // category
                var categoryAxis = chart.categoryAxis;
                categoryAxis.parseDates = true; // as our data is date-based, we set parseDates to true
                categoryAxis.minPeriod = "DD"; // our data is daily, so we set minPeriod to DD
                categoryAxis.dashLength = 1;
                categoryAxis.gridAlpha = 0.15;
                categoryAxis.position = "top";
                categoryAxis.axisColor = "#DADADA";

                // value                
                var valueAxis = new AmCharts.ValueAxis();
                valueAxis.axisAlpha = 0;
                valueAxis.dashLength = 1;
				// set label function which will format values
				valueAxis.labelFunction = formatLabel;
				
                chart.addValueAxis(valueAxis);

                // GRAPH
                var graph = new AmCharts.AmGraph();
                graph.title = "red line";
                graph.valueField = "visits";
                graph.bullet = "round";
                graph.bulletBorderColor = "#FFFFFF";
				graph.bulletBorderThickness = 2; 
                graph.lineThickness =...