struct ContentView: View {
 
    var body: some View {
        NavigationView {
            ScrollView {
              Text("Hello World")
                .navigationBarTitle("Good", displayMode: .inline)
            }
            .navigationBarColor(.green) // This is how you will use it
        }
    }
}

struct NavigationBarModifier: ViewModifier {
        
    var backgroundColor: UIColor?
    
    init( backgroundColor: UIColor?) {
        self.backgroundColor = backgroundColor
        
        let coloredAppearance = UINavigationBarAppearance()
        coloredAppearance.backgroundColor = self.backgroundColor ?? .clear
        UINavigationBar.appearance().standardAppearance = coloredAppearance // still global 

    }
    
    func body(content: Content) -> some View {
        ZStack{
            content
            VStack {
                GeometryReader { geometry in
                    Color(self.backgroundColor ?? .clear)
                        .frame(height: geometry.safeAreaInsets.top)
                        .edgesIgnoringSafeArea(.top)
                    Spacer()
                }
            }
        }
    }
}



extension View {
 
    func navigationBarColor(_ backgroundColor: UIColor?) -> some View {
        self.modifier(NavigationBarModifier(backgroundColor: backgroundColor))
    }
    
}