Avalonia/samples/ControlCatalog/Pages/TabbedPage/TabbedPageCustomizationPage.xaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="ControlCatalog.Pages.TabbedPageCustomizationPage">

  <UserControl.Styles>
    <Style Selector="TabbedPage TabControl">
      <Setter Property="Background" Value="{DynamicResource CustomBarBackgroundBrush}" />
    </Style>
    <Style Selector="TabbedPage TabItem">
      <Setter Property="Foreground" Value="{DynamicResource CustomUnselectedTabForegroundBrush}" />
    </Style>
    <Style Selector="TabbedPage TabItem:selected">
      <Setter Property="Foreground" Value="{DynamicResource CustomSelectedTabForegroundBrush}" />
    </Style>
  </UserControl.Styles>

  <DockPanel>
    <ScrollViewer DockPanel.Dock="Right" Width="260">
      <StackPanel Margin="12" Spacing="8">
        <TextBlock Text="Tab Customization" FontWeight="SemiBold" FontSize="16"
                   Foreground="{DynamicResource SystemControlHighlightAccentBrush}" />

        <TextBlock Text="Placement" FontSize="13" FontWeight="SemiBold" />
        <ComboBox x:Name="PlacementCombo" SelectedIndex="0"
                  SelectionChanged="OnPlacementChanged" HorizontalAlignment="Stretch">
          <ComboBoxItem Content="Top" />
          <ComboBoxItem Content="Bottom" />
          <ComboBoxItem Content="Left" />
          <ComboBoxItem Content="Right" />
        </ComboBox>

        <Separator />

        <CheckBox x:Name="ShowIconsCheck" Content="Show Icons"
                  IsCheckedChanged="OnShowIconsChanged" />

        <Separator />

        <TextBlock Text="Bar Background" FontSize="13" FontWeight="SemiBold" />
        <ComboBox x:Name="BarBgCombo" SelectedIndex="0"
                  SelectionChanged="OnBarBgChanged" HorizontalAlignment="Stretch">
          <ComboBoxItem Content="Default (theme)" />
          <ComboBoxItem Content="Blue (#1565C0)" />
          <ComboBoxItem Content="Green (#2E7D32)" />
          <ComboBoxItem Content="Purple (#6A1B9A)" />
          <ComboBoxItem Content="Dark (#212121)" />
        </ComboBox>

        <TextBlock Text="Selected Tab Color" FontSize="13" FontWeight="SemiBold" />
        <ComboBox x:Name="SelectedColorCombo" SelectedIndex="0"
                  SelectionChanged="OnSelectedColorChanged" HorizontalAlignment="Stretch">
          <ComboBoxItem Content="Default (accent)" />
          <ComboBoxItem Content="Red (#E53935)" />
          <ComboBoxItem Content="Orange (#F57C00)" />
          <ComboBoxItem Content="Teal (#00796B)" />
          <ComboBoxItem Content="Pink (#E91E63)" />
        </ComboBox>

        <TextBlock Text="Unselected Tab Color" FontSize="13" FontWeight="SemiBold" />
        <ComboBox x:Name="UnselectedColorCombo" SelectedIndex="0"
                  SelectionChanged="OnUnselectedColorChanged" HorizontalAlignment="Stretch">
          <ComboBoxItem Content="Default (theme)" />
          <ComboBoxItem Content="Gray (#757575)" />
          <ComboBoxItem Content="Light gray (#BDBDBD)" />
          <ComboBoxItem Content="White 60%" />
        </ComboBox>

        <Separator />

        <TextBlock Text="Disabled Tabs" FontSize="13" FontWeight="SemiBold" />
        <CheckBox x:Name="Tab0Check" Content="Home" IsChecked="True"
                  IsCheckedChanged="OnTabEnabledChanged" Tag="0" />
        <CheckBox x:Name="Tab1Check" Content="Search" IsChecked="True"
                  IsCheckedChanged="OnTabEnabledChanged" Tag="1" />
        <CheckBox x:Name="Tab2Check" Content="Settings" IsChecked="True"
                  IsCheckedChanged="OnTabEnabledChanged" Tag="2" />

        <Separator />

        <CheckBox x:Name="KeyboardCheck" Content="Keyboard Navigation" IsChecked="True"
                  IsCheckedChanged="OnKeyboardChanged" />
      </StackPanel>
    </ScrollViewer>

    <Border DockPanel.Dock="Right" Width="1" Background="{DynamicResource SystemControlForegroundBaseMediumLowBrush}" />

    <Border Margin="12"
            BorderBrush="{DynamicResource SystemControlForegroundBaseMediumLowBrush}"
            BorderThickness="1"
            CornerRadius="6"
            ClipToBounds="True">
      <TabbedPage x:Name="DemoTabs" TabPlacement="Top">
        <ContentPage x:Name="HomePage" Header="Home">
          <StackPanel Margin="16" Spacing="8">
            <TextBlock Text="Home" FontSize="24" FontWeight="Bold" />
            <TextBlock Text="Your personalized dashboard" TextWrapping="Wrap" Opacity="0.7" />
          </StackPanel>
        </ContentPage>
        <ContentPage x:Name="SearchPage" Header="Search">
          <StackPanel Margin="16" Spacing="8">
            <TextBlock Text="Search" FontSize="24" FontWeight="Bold" />
            <TextBox PlaceholderText="Type to search..." />
            <TextBlock Text="Search results will appear here." Opacity="0.7" />
          </StackPanel>
        </ContentPage>
        <ContentPage x:Name="SettingsPage" Header="Settings">
          <StackPanel Margin="16" Spacing="8">
            <TextBlock Text="Settings" FontSize="24" FontWeight="Bold" />
            <CheckBox Content="Enable notifications" />
            <CheckBox Content="Dark mode" />
            <CheckBox Content="Auto-save" IsChecked="True" />
          </StackPanel>
        </ContentPage>
      </TabbedPage>
    </Border>
  </DockPanel>
</UserControl>