Possibly an easier way to do this is to use a google gauge chart?
The two parts of the html:
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>
<script type="text/javascript">
google.charts.load('current', {'packages':['gauge']});
google.charts.setOnLoadCallback(drawChart);
function drawChart() {
var data = google.visualization.arrayToDataTable(
light list goes here
);
var options = {
width: 400, height: 400,
redFrom: 90, redTo: 100,
yellowFrom:75, yellowTo: 90,
minorTicks: 5
};
var chart = new google.visualization.Gauge(document.getElementById('chart_div'));
chart.draw(data, options);
}
</script>
</head>
<body>
<div id="chart_div" style="width: 400px; height: 120px;"></div>
</body>
</html>