Рони опередил
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script src="http://code.jquery.com/jquery-latest.min.js"></script>
<style>
html, body {
height: 100%;
}
</style>
</head>
<body>
<a href="#" class="link">Change color body</a>
<script>
var colors = ["red", "green", "blue", "yellow"], i = 0,
body = document.body,
link = document.querySelector('.link');
link.addEventListener('click', function(e) {
e.preventDefault();
body.style.backgroundColor = colors[i % colors.length];
i++;
});
</script>
</body>
</html>