primaryVariant property
A darker version of the primary color.
In Flutter SDK the primaryVariant color is only used by SnackBar button color in dark theme mode as a part of predefined widget behavior. If you provide a custom SnackBarThemeData where you define SnackBarThemeData.actionTextColor to primary or secondary, this color property becomes a good property to use if you need a custom color for custom widgets accessible via your application's ThemeData, that is not used as default color by any other built-in widgets. This applies to Flutter 2.8.1 and earlier versions.
The property is being deprecated in Flutter SDK and will be replaced by a new property called primaryContainer. It is deprecated from master v2.6.0-0.0.pre, but has not yet reached stable (2.8.1). See https://github.com/flutter/flutter/issues/89852.
If not defined, and if there is no colorScheme defined, it will be computed from primary color.
Implementation
final Color? primaryVariant;