code: public JFreeChartRender setGridPaint(Color color) {
          getPlot().setRangeGridlinePaint(color);
          getPlot().setDomainGridlinePaint(color);
          return this;
      }
docs: Sets color for grid in chart.
  <p/>
  Default grey.
  
  @param color new color for chart grid
  @return itself (fluent interface)