Starting November 27th, 2018, Google made some small changes to the appearance of the Google sign-in page. These follow changes made earlier this year, which updated the sign-in page to match the Material Design principles used in other Google products.
Specifically, you might notice outlines around some entry fields, and changes to the spacing and styling of other text on both the web and mobile screens. The changes started to take effect on November 27th and may take up to two weeks to reach all users.
