Untitled

<!doctype html>
<html lang="en">
<head>
  <style type="text/css">
.box {
        background-color:#FFFF00;
}
</style>

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>

</head>
<body>
  <script>
[].forEach.call( document.querySelectorAll('.box'), function(el) {
  el.style.color = 'red'; // or add a class
});
  </script>

<div class="box">
        This is red
        </div>

<script>
        $(‘.box’).css(‘color’, ‘red’);
</script>

</body>
</html>