LayoutTests/fast/dom/Window/window-screen-properties.html

<script>
if (window.layoutTestController)
    layoutTestController.dumpAsText();
</script>
The current pixel depth returned by window.screen.pixelDepth is:
<script>
document.write(window.screen.pixelDepth);
</script>
<br>
The current color depth returned by window.screen.colorDepth is:
<script>
document.write(window.screen.colorDepth);
</script>