Чтобы падало:
<style>
body {
margin:0px;
background: red;
}
div {
width: 100%;
height: 100%;
}
</style>
<body>
<div></div>
</body>
<script type="text/javascript" src="http://code.jquery.com/jquery.min.js"></script>
<script type="text/javascript">
$(function() {
var colorArr = ['red', 'green', 'blue'],
len = colorArr.length-1, i = 1;
$(function fallingColorBlocks() {
var bodyColor = i > 0 ? colorArr[i-1] : colorArr[len];
$("body").css({'background': bodyColor});
$("div").css({'display': 'none', 'background': colorArr[i]}).slideDown(1500,function(){
i < len ? i++ : i = 0;
fallingColorBlocks();
});
});
});
</script>