How do I change the colors on Y-Axis for values above, below zero? Chart.js 2.6

Using chart.js 2.6 Is there a way to dynamically change the bars in my chart for values above zero and below zero? The graph series data is being generated via a call to a method. Right now its just a random number generator but will be a DB call.

function changeWOWData(chart) {
    var datasets = chart.data.datasets;
    var labelLen = chart.data.labels.length;
    if (datasets[0]) {
        for (i = 0, len = datasets.length; i < len; i++) {
            try {
                for (j = 0, len = labelLen; j < len; j++) {
                    datasets[i].data[j] = getRandomInt(-100, 100);
                }

            } catch (e) {
                console.log(e.message);
            }
        }
    }
}

Chart looks like this:

I want the chart bars above zero to be blue, the bars below zero to be red.

Any/all replies appreciated. Thanks in advance!

Griff

** Edit ** Added the code from the answer below as such:

var myBarChart = new Chart(wowChart, {
    type: 'bar',
    data: wowData,
    plugins: [{
        beforeDraw: function (c) {
            var data = c.data.datasets[0].data;
            for (var i in data) {
                try {
                    var bar = c.data.datasets[0]._meta[0].data[i]._model;
                    if (data[i] > 0) {
                        bar.backgroundColor = '#07C';
                    } else bar.backgroundColor = '#E82020';

                } catch (ex) {
                    console.log(ex.message);
                }
                console.log(data[i]);
            }
        }
    }],
    options: wowOptions
});

Every other line of the console I see the data element along with the exception

Solution

You could accomplish that using the following chart plugin :

plugins: [{
   beforeDraw: function(c) {
      var data = c.data.datasets[0].data;
      for (let i in data) {
         let bar = c.data.datasets[0]._meta['0'].data[i]._model;
         if (data[i] > 0) {
            bar.backgroundColor = '#07C';
         } else bar.backgroundColor = '#E82020';
      }
   }
}]

^{add this followed by your chart options}

ᴅᴇᴍᴏ

var ctx = document.getElementById("canvas").getContext('2d');
var myChart = new Chart(ctx, {
   type: 'bar',
   data: {
      labels: ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun'],
      datasets: [{
         label: 'LEGEND',
         data: [9, 14, -4, 15, -8, 10]
      }]
   },
   options: {},
   plugins: [{
      beforeDraw: function(c) {
         var data = c.data.datasets[0].data;
         for (let i in data) {
            let bar = c.data.datasets[0]._meta['0'].data[i]._model;
            if (data[i] > 0) {
               bar.backgroundColor = '#07C';
            } else bar.backgroundColor = '#E82020';
         }
      }
   }]
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.6.0/Chart.min.js"></script>
<canvas id="canvas" height="180"></canvas>