Try this
<Style x:Key="ListItemStyle" TargetType="{x:Type ListBoxItem}">
<Setter Property="OverridesDefaultStyle" Value="True" />
<Setter Property="MinHeight" Value="30" />
<Setter Property="Foreground" Value="Black" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListBoxItem}">
<Border BorderBrush="#FF66AFDE" BorderThickness="0 0 0 1" x:Name="border">
<ContentPresenter/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsFocused" Value="True">
<Setter TargetName="border" Property="Background" Value="Red"></Setter>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I hope this will help