How to change color of back button on NavigationView

I was trying to do the same for a while, and do not think there is SwiftUI solution yet. One of things that will get work done though (if it works for your use case) is UIKit's appearance:

UINavigationBar.appearance().tintColor = .black

You can use the accentColor property on the NavigationView to set the back button color, like in this example:

var body: some View {
    NavigationView {
        List(1..<13) { item in
            NavigationLink(destination: Text("\(item) x 8 = \(item*8)")) {
                Text(String(item))
            }
        }.navigationBarTitle("Table of 8")
    }.accentColor(.black) // <- note that it's added here and not on the List like navigationBarTitle()
}