labelTextStyle property
final
/ The text style of the label.
If null, NavigationBarThemeData.labelTextStyle is used. If that is also null, the default text style is TextTheme.labelMedium with ColorScheme.onSurface when the destination is selected, and ColorScheme.onSurfaceVariant when the destination is unselected, and ColorScheme.onSurfaceVariant with an opacity of 0.38 when the destination is disabled.
If ThemeData.useMaterial3 is false, then the default text style is TextTheme.labelSmall with ColorScheme.onSurface.
Implementation
final MaterialStateProperty<TextStyle?>? labelTextStyle;