Gmail is the latest app to launch the dark-mode for iOS 13. Google started rolling out Gmail’s dark-mode to selected users in September but the update has started to seed to all users.
Dark-mode has been proven to enhance battery life and since the launch of iOS 13 app developers around the world are introducing this feature in their apps.
You should have received the latest update of the app, if not, you’ll update soon.
This is activated automatically when dark mode is enabled on your device however you can also toggle this manually To do that, simply tap Settings in the Gmail app then go to Themes and select what you want.