green top-level property Null safety

Implementation

NBColor green = const NBColor(
    0xff22c55e,
    <String, Color>{
      'green.50 ': Color(0xfff0fdf4),
      'green.100': Color(0xffdcfce7),
      'green.200': Color(0xffbbf7d0),
      'green.300': Color(0xff86efac),
      'green.400': Color(0xff4ade80),
      'green.500': Color(0xff22c55e),
      'green.600': Color(0xff16a34a),
      'green.700': Color(0xff15803d),
      'green.800': Color(0xff166534),
      'green.900': Color(0xff14532d),
    },
    'green');