// 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';
}
document.body.style.backgroundColor = "yellow";function changeBackground(color) {
document.body.style.background = color;
}
window.addEventListener("load",function() { changeBackground('red') });var warning = document.getElementById("warning");
warning.style.background-color = "red";
document.querySelector('html').style.backgroundColor = 'red';Changing body background color using javascript