foregroundColor property
final
The default foreground color for icons and text within the button.
If this property is null, then the FloatingActionButtonThemeData.foregroundColor of ThemeData.floatingActionButtonTheme is used. If that property is also null, then the ColorScheme.onPrimaryContainer color of ThemeData.colorScheme is used. If ThemeData.useMaterial3 is set to false, then the ColorScheme.onSecondary color of ThemeData.colorScheme is used.
Implementation
final Color? foregroundColor;