Change background color or image with Javascript

Change background color

Here is the HTML:

<input type="button" onClick="changecolor('red');" value="red">
<input type="button" onClick="changecolor('green');" value="green">
<input type="button" onClick="changecolor('blue');" value="blue">

Here is the Javascript:

<script type="text/javascript">
function changecolor(color){
document.bgColor = color;
}
</script>