Custom theme light and dark

I’m looking to how create a custom theme that change based on OS light or dark preference.

In the extension to create a custom theme I don’t see the possibility to specify colors for light and for dark theme.

When Windows is switched to dark mode my custom theme still be light.
How can I set a color combinations also for the dark mode?

I tried to look at the documentation but I found only CSS code that I think cannot work in the manifest.json of the theme.

thank you for the help.