JFreeChart setDefaultFillPaint not working

Question

I tried the following code to change the color below my graph line to green:

I dont know why JFreeChart just ignores my wanted color - but I get no error.

        JFreeChart chart = ChartFactory.createLineChart(
                "# of Sales by Month",   // chart title
                "Month",                       // domain axis label
                "# of Sales",                   // range axis label
                dataset,                         // data
                PlotOrientation.VERTICAL,        // orientation
                true,                           // include legend
                true,                            // tooltips
                false                            // urls
        );

        chart.setBackgroundPaint(Color.BLUE);

        CategoryPlot plot = (CategoryPlot) chart.getPlot();
        plot.setRangePannable(true);
        plot.setRangeGridlinesVisible(true);
        plot.setBackgroundAlpha(1);
        plot.setBackgroundPaint(Color.BLUE);
        //        Paint p = new GradientPaint(0, 0, Color.white, 1000, 0, Color.green);
        //        plot.setBackgroundPaint(p);


        NumberAxis rangeAxis = (NumberAxis) plot.getRangeAxis();
        rangeAxis.setStandardTickUnits(NumberAxis.createIntegerTickUnits());

        chart.getCategoryPlot().getRenderer().setDefaultFillPaint(Color.GREEN);
        ChartUtils.applyCurrentTheme(chart);

        LineAndShapeRenderer renderer = (LineAndShapeRenderer) plot.getRenderer();
        renderer.setDrawOutlines(true);
        renderer.setSeriesStroke(0, new BasicStroke(3.0f));
        renderer.setSeriesOutlineStroke(0, new BasicStroke(2.0f));
        renderer.setSeriesShape(0, new Ellipse2D.Double(0, 0, 0, 0));
        return chart;

The problem is, that it doesnt change, i cant find any way to fix that