blueGray top-level property Null safety

Implementation

NBColor blueGray = const NBColor(
    0xff64748b,
    <String, Color>{
      'blueGray.50 ': Color(0xfff8fafc),
      'blueGray.100': Color(0xfff1f5f9),
      'blueGray.200': Color(0xffe2e8f0),
      'blueGray.300': Color(0xffcbd5e1),
      'blueGray.400': Color(0xff94a3b8),
      'blueGray.500': Color(0xff64748b),
      'blueGray.600': Color(0xff475569),
      'blueGray.700': Color(0xff334155),
      'blueGray.800': Color(0xff1e293b),
      'blueGray.900': Color(0xff0f172a),
    },
    'blueGray');