Basic line

by Black Label

HTML

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

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

JavaScript

let data = [];
 for (let i = 0; i < 300; i++) {
   data.push(Math.ceil(Math.random() * 90));
 }

 let start = +new Date(),
   text = document.getElementById('text');


 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: data
   }],
 });
 text.innerHTML += `Finished rendering chart after ${new Date() - start} ms. <br>`