Comment 4 for bug 1853768

Just a bit of context:
Symbolic action icons are the de-facto in a GNOME environment, full-colour icons are legacy, that's why Yaru theme didn't originally have any "legacy" full-colour action icons as its original author refused to do so.
The recent addition of the coloured document-*.png icons in Yaru is just a workaround for Qt apps in order not to appear broken under Yaru. And not all full-colour icons will be in Yaru, only the needed document-*.png ones.