Dynamically / Programmically create chart ColumnSeries

Each chart has a series property which is an Array of all of the series
(surprise). You can add new series dynamically using addItem:

var column = new ColumnSeries();
column.yField = "population"; // assuming that is the field in the
dataProvider you want to graph
// set other ColumnSeries values, see the Flex documentation
column.setStyle("fill", new SolidColor(0xFF0000,100)); // bright red
column.setStyle("renderer", new SimpleBoxRenderer); // only if you don't want
a ShadowBoxRenderer which is the default
myChart.series.addItem(column);

For the fill, you can also use a Gradient - see the Flex documentation for
details.