type 'Color' is not a subtype of type 'MaterialColor' what is this code example

Example: Unhandled Exception: type 'Color' is not a subtype of type 'MaterialColor'

Map<int, Color> color = {
50: Color.fromRGBO(255, 92, 87, .1),
100: Color.fromRGBO(255, 92, 87, .2),
200: Color.fromRGBO(255, 92, 87, .3),
300: Color.fromRGBO(255, 92, 87, .4),
400: Color.fromRGBO(255, 92, 87, .5),
500: Color.fromRGBO(255, 92, 87, .6),
600: Color.fromRGBO(255, 92, 87, .7),
700: Color.fromRGBO(255, 92, 87, .8),
800: Color.fromRGBO(255, 92, 87, .9),
900: Color.fromRGBO(255, 92, 87, 1),
};

MaterialColor colorCustom = MaterialColor(0xFFFF5C57, color);