That explains why Notebook was stuck with a green one. I don't know if it's a bug in his browser (I'm assuming he's using FireFox cos I've seen a similar problem when bookmarking sites), or if the browser just loads the same icon file name from the cache and doesn't do any other checks......
Also, I did a Ctrl+F5 to make sure the site reloads fresh content (works in FF, don't know about other browsers) and the icon did not show up. If you replaced the file over FTP, the change should be immediate.