Google's own Now Launcher in the Play Store used to mimic the graphical design of whatever version of Android your particular handset is running when you install it, but with the latest update to the app this is no more. Going forward, those who are primed to use the official Google Now launcher, and the Search app that is its core component, will be looking at Lollipop's Material Design language, regardless of which Android version they are running.
The Search field that stays at the top of the Google Now launcher has turned white, as it went with the latest Android 5.0, and there are new animations. Other than those you won't be noticing much head-on visual changes. The Google Now section, however, has been updated with a panel that can be swiped in from the left, allowing you to change the launcher's settings, quickly move between accounts, and set reminders.