JFreeChart _chart = ChartFactory.createTimeSeriesChart(......);
XYPlot _xyplot=(XYPlot) _chart.getPlot();
XYLineAndShapeRenderer xylinerenderer=(XYLineAndShapeRenderer)_xyplot.getRenderer();
//以下分别给同一个曲线图中3条曲线设置颜色,0为第一条1为第二条,2为第三条
xylinerenderer.setSeriesPaint(0, new Color(0, 0 ,255 )); 或者 xylinerenderer.setSeriesPaint(0, Color.BLUE);
xylinerenderer.setSeriesPaint(1, new Color(255 ,215, 0 ));
xylinerenderer.setSeriesPaint(2, new Color(0, 238, 118));