Customizing the Theme of the Account in Android
Themes are an important aspect of the user interface. Users can customize the themes from the settings.
To customize the theme of the account
Click the Hamburger Menu 
> Settings 
> Themes.
Color theme - Select a colour to customize the appearance of the app.
Follow device theme - Set the app's theme to match that of the device. For example, if the device is set to Dark Theme, then the app will also follow the Dark Theme.
Set dark theme - Set the app to a darker interface.