Change background color when user logs in and out

Site could be found at http://trade.edicy.co/

Currently, it has the most basic implementation of the FB log-in button that automatically turns into a log out button after authentication. Now I want the background to change color once the user logs-in and revert back after the user logs-out.

Also is it possible to move the position and size of the Facebook picture far from the log-in button after log-in?

Thanks in advance.

You can capture the auth.statusChange event via the FB.Event.subscribe function of the JS SDK. See https://developers.facebook.com/docs/reference/javascript/FB.Event.subscribe/#login-logout for a description. Additionally, you can have a look at https://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus

For example

var loginCallback= function(response) {

    if (response.status === 'connected') {
    // the user is logged in and has authenticated your
    // app, and response.authResponse supplies
    // the user's ID, a valid access token, a signed
    // request, and the time the access token 
    // and signed request each expire

      document.body.style.background = "red";

    } else if (response.status === 'not_authorized') {
        // the user is logged in to Facebook, 
        // but has not authenticated your app
    } else {
        // the user isn't logged in to Facebook.
        document.body.style.background = "green";
    }

}

// In your onload handler add this call
FB.Event.subscribe('auth.statusChange', loginCallback);