I need to change background color to white of the displayed page if . Is that possible? Now background of the original website is g
It is possible. With vanilla Javascript, you can use the function below for reference.
function updateIframeBackground(iframeId) {
var x = document.getElementById(iframeId);
var y = (x.contentWindow || x.contentDocument);
if (y.document) y = y.document;
y.body.style.backgroundColor = "#2D2D2D";
}
https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_iframe_contentdocument