TabView with different TabBar backgroundColor on each Tab SwiftUi

I can't seem to get this simple problem working. I have a TabView with multiple Tabs, where depending on the selectedTab, the TabBar should have a different background. It should look like this, but this won't work, any help would be highly appreciated:

TabView(selection: $selectedTab){
   NavigationView{
      Home()
   }
   .navigationViewStyle(StackNavigationViewStyle())
   .tabItem{
            Image(systemName: "house")
   }.tag("home")
   .onAppear{
       UITabBar.appearance().backgroundColor = UIColor.white
   }
    

   NavigationView{
      Post()
   }
   .navigationViewStyle(StackNavigationViewStyle())
   .tabItem{
            Image(systemName: "plus")
   }.tag("plus")
   .onAppear{
       UITabBar.appearance().backgroundColor = UIColor.clear
   }
}