Highcharts test tool
HTML
<script src="http://code.highcharts.com/highcharts.js"></script>
<script src="http://code.highcharts.com/modules/exporting.js"></script>
<div id="container"></div>
CSS
#container {
min-width: 300px;
max-width: 800px;
height: 300px;
margin: 1em auto;
}
JavaScript
var color = Highcharts.Color(Highcharts.getOptions().colors[0]).brighten(0.1),
rgba = color.rgba;
console.log('#' + rgba[0].toString(16) + rgba[1].toString(16) + rgba[2].toString(16));