To save your mobile device's battery, you can use the dark theme in Google Chat.
- Open the Chat app .
- At the top, tap Menu Settings .
- Tap Theme.
- Select the theme for this device:
- Light—White background with dark text.
- Dark—Black background with light text.
- System default—Uses the iOS device's setting.
Changing the theme in Chat doesn't change the theme in any other apps.