A custom TabBar where you can control the color behind the Tabs

colored_tab_bar.dart

class ColoredTabBar extends Container implements PreferredSizeWidget {
  ColoredTabBar({@required this.color, this.tabBar, this.header});

  final Color color;
  final TabBar tabBar;
  final Widget header;

  @override
  Size get preferredSize =>
      tabBar?.preferredSize ?? Size(double.infinity, 48.0);

  @override
  Widget build(BuildContext context) {
    return Material(
      color: color,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceAround,
        children: <Widget>[
          Padding(padding: EdgeInsets.only(top: header != null ? 10 : 0)),
          header ?? Container(),
          tabBar ?? Container(),
        ],
      ),
    );
  }
}