Go4Expert - background color change problem

This is my first time using JavaScript, and I found a tutorial online to learn off of. Here is the code I have made, meant to make three buttons, each of which change the background color of the window.

Code:

<html>

<head>



<SCRIPT LANGUAGE="JavaScript">



function BgColor (color) {

document.bgColor=color }



</SCRIPT>

</head>



<body>

<form>

<input type="button" name="redbutton" value="Red" onClick="changecolor ('red')">



<input type="button" name="bluebutton" value="Blue" onClick="changecolor ('blue')">



<input type="button" name="greenbutton" value="Green" onClick="changecolor ('green')">

</form>



</body>

</html>

The problem is, whenever you hit a button, nothing at all happens. Any help, please?