Animating the document background color after every defined interval

<script language = "javascript" type="text/javascript">
function change_document_bg_color()
{
   setTimeout("document.bgColor = 'blue'", 1000)
   setTimeout("document.bgColor = 'pink'", 2000)
   setTimeout("document.bgColor = 'yellow'", 2500)
   setTimeout("document.bgColor = 'red'", 3000)
   setTimeout("document.bgColor = 'cyan'", 4000)
}
</script>