To get the current colour scheme from the CLI, use the following command:
defaults read -g AppleInterfaceStyle
If MacOS is in dark mode, this will print
Dark. But if MacOS is in light mode, this key won’t be set at all, and the command will print return an error of the form:
2022-10-04 09:15:18.058 defaults[35844:466643] The domain/default pair of (kCFPreferencesAnyApplication, AppleInterfaceStyle) does not exist
As such, in order to confirm that the colour scheme is light, you’ll need to parse for this error.