Basic line

by Black Label

HTML

<script src="https://code.highcharts.com/highcharts.js"></script>

<div id="container" style="height:300px"></div>

JavaScript

Highcharts.chart('container', {
  chart: {
    events: {
      load: function() {
        let data = this.series[0].data
        data.forEach(el => {
          if (el.y >= 25) {
            el.update({color:'red'})
          }
        })
      },
    },
  },
  series: [{
    data: [2, 5, 1, 6, 7, 8, 5, 5, 35, 34, 34, 63, 46, 34, 4, 53, 34]
  }],
});