Google is changing the look of sign-in on the web soon, according to the notification that's been posted over on Google Support for learning about the sign-in page. Google has already updated the look of the sign-in page on the mobile side of things, but hadn't yet changed the visuals for the web version. Google says that over the next few weeks that's about to change although they don't mention exactly when they will start the transition, and it isn't made clear whether they'll simply flip the switch and the visuals will be changed for everyone at once or whether the new look will roll out to users in stages.
While the visuals of the sign-in page are changing there are things that won't change. Google assures users that just like with the mobile page, the way you sign-in won't be changed at all as you'll still use the same steps as before and you'll still be able to sign in securely. The new sign-in page will bring a cleaner design to things though, and Google notes that signing in will be faster than before which means you'll save a precious second or two when signing into your account. This will also make for a consistent visual appearance across phones, tablets, and computers, which is one of the bigger reasons for the change as Google wants a streamlined look. The new visual design of the sign-in page will incorporate parts of Material Design which will be part of what introduces the more consistent style.
In addition to notifying users via the Google Support page, the current sign-in page also shows a brief message that will alert users to the new changes that are coming in the near future so it should be hard to miss unless you never sign in to your account. That being said, the change is just around the corner so whether you notice it before it happens or not, it isn't too far out and everything will continue to work as normal. Changing the look of the sign-in page isn't a major thing but even the smallest things can be beneficial.