How to use the light "Default" theme?

[Franpa]

1) Firefox has 2 light themes and 1 dark theme included with the web browser: Default (variation of Light), *Light, Dark.
2) Configuring the Windows 10 O/S to use the Dark setting for Apps will cause Firefox 63 to change the appearance of the Default theme to match the Dark theme.
3) I can no longer access the Default (variation of Light) theme as seen in the top image here https://imgur.com/a/3snQAPK because Default and Dark are now the same as each other.
*4) I hate the Light theme because it is lacking in contrast between the Bookmarks and Tab bar as well as lacking contrast between the URL and Menu bar. It makes it annoyingly harder to identify with a glance the different UI elements.

You can see both the Light and Default (variation of Light) themes here, I want access to the theme in the top image while the O/S is set to the Dark setting for Apps: https://imgur.com/a/3snQAPK

[Brummelchen]

why dont you "enable" it right side?

[jscher2000]

Is this an accurate summary:

"I would like the toolbar background color used by the Light theme to be the color that was used by the Default theme with a light Windows 10 theme."

I don't know what color that was, but it seems like something that either an add-on theme (solid color) or a custom style rule added to your userChrome.css file could do for you.

[Franpa]

Is this an accurate summary:

"I would like the toolbar background color used by the Light theme to be the color that was used by the Default theme with a light Windows 10 theme."

Yeah, that's an accurate summary.