As usual, today morning I opened gmail.com to check my mails. I noticed a small yellow bar saying
Coming soon: A new sign-in page! Preview it Learn more
The new look is like Gmail Preview theme or like Google Plus. The new sign-in page will be rolled out for all Google products (like gmail, youtube, Google docs etc) in few days. The change is part of a larger redesign of Google products.
Below is direct link of Google new sign-in page.