2020-05-21-multicolor-tweening-in-flutter_widget_state.dart

class _TweenSequenceBoxState extends State<TweenSequenceBox>
    with SingleTickerProviderStateMixin {
  AnimationController _controller;
  Animation<Color> _colorAnim;

  @override
  void initState() {
    super.initState();

    _controller = AnimationController(
      duration: const Duration(seconds: 5),
      vsync: this,
    )..forward()..repeat();

    _colorAnim = bgColor.animate(_controller);
  }

 // Our build method will go here

 @override
  void dispose() { // don't forget to clean up!
    _controller.dispose();
    super.dispose();
  }

}