How to theme dialogs of slackpkg/sbopkg?

I have recently started to use a Nord[1]-themed terminal emulator. midnight commander looked ugly and blurry, but I managed to fix that by changing the theme from its settings.

Now I have the same problem with slackpkg/sbopkg (which are dialog-based I believe). How to tune the visual appearance of such programs? Either my searching skills are too weak, or the dialog word is too general, but I couldn't find anything relevant so far.

1. https://www.nordtheme.com/