how to change background color in javascript w3schools

 // change background color for specific id ..
function changebackground(){
	document.getElementById('id').style.backgroundColor = 'green' ; 
}
// change background color for whole body..
function changebackground(){
	document.body.style.backgroundColor = 'green';
}
 var element = document.body;
element.style.backgroundColor = "blue";function changeBackground(color) {
   document.body.style.background = color;
}

window.addEventListener("load",function() { changeBackground('red') });var warning = document.getElementById("warning");
  warning.style.background-color = "red";