selectedIconTheme property
The size, opacity, and color of the icon in the currently selected BottomNavigationBarItem.icon.
If this is not provided, the size will default to iconSize, the color will default to selectedItemColor.
It this field is provided, it must contain non-null IconThemeData.size and IconThemeData.color properties. Also, if this field is supplied, unselectedIconTheme must be provided.
Implementation
IconThemeData? selectedIconTheme;