unobtrusive feedback when the page is loaded (onload)

I added this script in the footer of my page that will flash the usually black background of the page once the page is loaded:

<script>$(document).ready(function() {        function highlight_background(){            if(document.getElementById('content')) {                //fading background:                $('#content').css({backgroundColor:"#081108"});                $('#content').animate({backgroundColor: "black"}, 2000);            }         }         highlight_background();)}</script>

This looks great on black background like in my space online game.

But now I am planning to implement a feedback for the user in a serious application of a customer of mine that has white background. there it looks too playful.

Any idea how to manage an unobstrusive feedback once the page is loaded?