您可以为最后一个系列启用colorByPoint选项：

series: [..., {
    ...,
    colorByPoint: true
  }]

现场演示：https://jsfiddle.net/BlackLabel/fdwbLzan/
API引用：https://api.highcharts.com/highcharts/series.column.colorByPoint

或者为每个点定义单独的颜色：

series: [..., {
    ...,
    data: [{
      y: 3,
      color: 'black'
    }, {
      y: 4,
      color: 'purple'
    }, {
      y: 4,
      color: 'green'
    }, {
      y: 2,
      color: 'orange'
    }, {
      y: 5,
      color: 'blue'
    }]
  }]

现场演示：https://jsfiddle.net/BlackLabel/r87mv6n3/
API参考：https://api.highcharts.com/highcharts/series.column.data.color