anchor.diff:    /// A darker version of the secondary color.
     final Color secondaryVariant;
   
  +  /// The background color for widgets like [Card].
  +  final Color surface;
  +
     /// A color that typically appears behind scrollable content.
     final Color background;
   
  
positive.code:   /// [InputDecoration.errorText].
    final Color error;
  
    /// The background color for widgets like [Card].
    final Color surface;
  
    /// A color that's clearly legible when drawn on [primary].
    final Color onPrimary;
  
    /// A color that's clearly legible when drawn on [secondary].
    final Color onSecondary;
  
    /// A color that's clearly legible when drawn on [surface].
    final Color onSurface;
  
    /// A color that's clearly legible when drawn on [error].
    final Color onError;
  
    /// A color that's clearly legible when drawn on [background].
    final Color onBackground;
  
    /// The overall brightness of this color scheme.
    final Brightness brightness;
  
negative.code: 
    /// Create a color scheme from a [MaterialColor] swatch.
    ///
    /// This constructor is used by [ThemeData] to create its default
    /// color scheme.
    factory ColorScheme.fromSwatch({
      MaterialColor primarySwatch = Colors.blue,
  