/usr/share/themes/Greybird/gtk-3.0/gtk-contained-dark.scss is in greybird-gtk-theme 3.22.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | $variant: 'dark';
@import 'colors';
@import 'drawing';
@import 'common';
@import 'colors-public';
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