plotBands property
Render the plot band in axis.
Widget build(BuildContext context) {
    return Container(
        child: SfCartesianChart(
           primaryXAxis: NumericAxis(
             plotBands:
 <PlotBand>[PlotBand(start:20, end:30, color:Colors.red, text:'Flutter')]
               ),
        )
    );
}
Implementation
final List<PlotBand> plotBands;