在使用charts_flutter包时，如何使用从提供程序文件中获取的值设置条形图的颜色

import 'package:charts_flutter/flutter.dart' as charts;
import 'package:provider/provider.dart';

class ChartData {
  final String name;
  final double value;

  ChartData(this.name, this.value);
}

class MyProvider with ChangeNotifier {
  List<ChartData> _dataList = [
    ChartData('Category A', 50),
    ChartData('Category B', 75),
    ChartData('Category C', 30),
  ];

  List<ChartData> get dataList => _dataList;
}

var provider = Provider.of<MyProvider>(context);

var series = [
  charts.Series(
    id: 'Category',
    data: provider.dataList,
    domainFn: (ChartData data, _) => data.name,
    measureFn: (ChartData data, _) => data.value,
    colorFn: (ChartData data, _) =>
        charts.ColorUtil.fromDartColor(_getColor(data.value)),  // 调用获取颜色的函数
  ),
];

Color _getColor(double value) {
  if (value >= 70) {
    return Colors.green;
  } else if (value >= 50) {
    return Colors.orange;
  } else {
    return Colors.red;
  }
}

return charts.BarChart(
  series,
  animate: true,
  // 其他配置项...
);