It has been three years since Google changed their favicon to the multi colored icon we have today. But now we are seeing reports of some users reporting a new all blue favicon being tested by Google.
The image to the right show off the new all blue Google Favicon. You can see it at google.com/images/google_favicon_128.png as well, to prove this is something Google is hosting.
It looks the same structurally as the colored one most of us see today - but this is one is all blue. Here is an enlarged colored favicon:
That launched in January 2009, between May 2008 – January 2009 we had the blue lowercase G, and from who knows when till May 2008 we had the classic G with colored box. Here is the history of those icons in the URL bar.
I am not sure if Google will go all blue soon or if this is for a specific Google property only.
Forum discussion at Google Blogoscoped Forums.