As for iOS13.0 and iOS13.1, I can see a difference in behaviour when using a SearchController:
-> in iOS12.x, the BackButton is correct in Yellow
-> in iOS13.0, the BackButton is correct in Yellow
-> in iOS13.1, the BackButton is wrong (in default-Blue)
The backButton turns into the wrong color if the user types a few Search-Letters and then presses Cancel.
In addition, I set the color as follows (..not working for iOS13.1):
navigationItem.searchController?.searchBar.barStyle = .black
navigationItem.searchController?.searchBar.keyboardAppearance = .dark
navigationItem.searchController?.searchBar.tintColor = .yellow
navigationItem.searchController?.searchBar.barTintColor = .yellow
I experienced this exact issue as well and it has been fixed on iOS 13.2