<html>
<head>
<style>
html {
  -webkit-filter: brightness(1.1) contrast(120%);
}
#rect {
  background: red;
  width:  100px;
  height:  100px;
}
</style>
</head>
<body>
<div id="rect"></div>
</body>
<script>
function changeBackground() {
    document.getElementById("rect").style.background = "green";
}

if (window.testRunner) {
    testRunner.dumpAsText(true);
    testRunner.display();
    changeBackground();
} else 
    window.setTimeout(changeBackground, 250);

</script>
</html>