Avalonia/samples/XamlTestApplicationPcl/ListBoxItem.paml

<Styles xmlns="https://github.com/perspex">
  <Style Selector="ListBoxItem">
    <Setter Property="Template">
      <ControlTemplate>
        <Border Name="border"
                Background="{TemplateBinding Background}"
                BorderBrush="{TemplateBinding BorderBrush}"
                BorderThickness="{TemplateBinding BorderThickness}">
          <ContentPresenter Name="PART_ContentPresenter"
                            Content="{TemplateBinding Content}"
                            Margin="{TemplateBinding Padding}"/>
        </Border>
      </ControlTemplate>
    </Setter>
  </Style>
  <Style Selector="ListBoxItem:selected /template/ Border#border">
    <Setter Property="Background" Value="#fff0f0f0"/>
  </Style>
  <Style Selector="ListBoxItem:selected:focus /template/ Border#border">
    <Setter Property="Background" Value="#ffd0d0d0"/>
  </Style>
</Styles>