ey_cloud_prod.user.js

// ==UserScript==
// @match        https://cloud.engineyard.com/*
// @version      2
// ==/UserScript==

// a function that loads jQuery and calls a callback function when jQuery has finished loading
function addJQuery(callback) {
  var script = document.createElement("script");
  script.setAttribute("src", "//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.min.js");
  script.addEventListener('load', function() {
    var script = document.createElement("script");
    script.textContent = "window.jQ=jQuery.noConflict(true);(" + callback.toString() + ")();";
    document.body.appendChild(script);
  }, false);
  document.body.appendChild(script);
}

function main() {
  if($('#app .environment-name').text().indexOf('production') >= 0){
    background = {
      'background-color': "rgba(255, 0, 0, 0.55)",
      'background-image': "url('http://i.imgur.com/i8KY7.gif')",
      'background-position': 'left top',
      'background-repeat': 'repeat'
    }
    $('#content').css(background)
    $('.page').css('background-color', 'white')
  }

  document.title = $('#app .environment-name').text().trim().split(/\n/)[0];
}

addJQuery(main)

Download and drag this file into chrome://extensions/ with "Developer Mode" checked to install in Google Chrome.