html

<html>
<head>

    <link rel="stylesheet" type="text/less" href="style.less" />
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/less.js/1.4.1/less.min.js"></script>
    <script>
    function myFunction() {
        setInterval(function(){
            less.modifyVars({
                '@base': '#00ff00',
            });
        },3000);
    }
    </script>
</head>
<body>
    <button onclick="myFunction()">Probeeeer</button>
</body>

</html>