How to make color long last on Navigation Bar on Flutter?

I would like to build a bottom navigation bar, with selected icon item showing a customized color and unselected icon items in white. But after I set up a setState() function for the hook that indicates the item index, the click only makes the color show an instant and disappears. However, when I use Colors, the pre-set system palette colors, for example Colors.amber[800], it works out fine and the color will STAY. Instead when I use my own color, it will FLASH. What is the probable cause for the situation and what is the fix?

Here’s my code and issue demo GIF.

class _MyRootPageState extends State<MyRootPage> {
  int currentPage = 0;
  List<Widget> pages = const [
    HomePage(),
    SettingsPage(),
    SavedPage(),
    ShoppingCartPage(),
    MessagePage()
  ];

  void setCurrentPage(int index) {
    // setState() refreshes the component tree
    setState(() {
      currentPage = index;
    });
  }

  @override
  Widget build(BuildContext context) {

    return Scaffold(
      appBar: AppBar(
        title: const Text('Pink Blue'),
      ),
      body: pages[currentPage],
      bottomNavigationBar:BottomNavigationBar(
        showSelectedLabels: false,
        showUnselectedLabels: false,
        backgroundColor: Colors.white,
        items: const [
          BottomNavigationBarItem(icon: Icon(Icons.home_outlined), label:"",),
          BottomNavigationBarItem(icon: Icon(Icons.search), label:""),
          BottomNavigationBarItem(icon: Icon(Icons.list), label:""),
          BottomNavigationBarItem(icon: Icon(Icons.account_circle_outlined), label:""),
          BottomNavigationBarItem(icon: Icon(Icons.mail), label:""),
        ],
        onTap: setCurrentPage,
        currentIndex: currentPage,
        selectedItemColor: const Color(0xE10098),
      ),
    );
  }
}