<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("h1, h2, p").toggleClass("blue");
});
});
</script>
<style>
.blue {
color: blue;
}
</style>
</head>
<body>
<h1>Heading 1</h1>
<h2>Heading 2</h2>
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
<button>Toggle class</button>
</body>
</html>