Also worth noting is that dark mode has been available in the Google app in beta form for months. It's also been available in small amounts to non-beta users for a little while.
Today however marks the rollout to all non-beta users who have Android 10 installed.
With the new dark mode feature, the app will match the default theme (light or dark) of the system. The option will also now be there to turn dark mode on or off.
The Google app now has a dark mode toggle
The main change here for users that have had dark mode in this app for a while is the toggle.
If you have your system theme set to light, you can go into settings and then general to find the theme option all the way at the bottom of that page. Here you can set the Google app to dark or light depending on your preference.
This way the app presents a look that isn't tied to whatever you have set for the system theme. Though, if you have the system theme set to dark already, chances are you probably want the dark theme for any app that can support it.
And it would just be easier to leave it set to system default. That said it never hurts to have the option to change it between light and dark regardless of the system theme.
The rollout starts today but will continue over the next few days
Some non-beta users of the Google app will start to see the darker theme toggle today.
The rollout is probably going to take the next few days though to hit all users who have Android 10 running on their devices. So if you don't see the option to toggle dark mode right away then it may not have hit your device yet.
Of course the Google app should still appear with the darker look if you have the system default set to dark.
One by one Google has implemented a dark mode across its different apps. As more of them offer the feature, you'll have the option to leave the system theme in the light mode and then toggle dark for just the apps that you want to have it.