Adding to @Sheridan’s answer
This isn’t a 100% accurate but should get you pretty close (it’s using the colors from GridView
which is pretty close to Windows Explorer)
<TreeView ...>
<TreeView.Resources>
<LinearGradientBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" EndPoint="0,1" StartPoint="0,0">
<GradientStop Color="#FFD9F4FF" Offset="0"/>
<GradientStop Color="#FF9BDDFB" Offset="1"/>
</LinearGradientBrush>
<LinearGradientBrush x:Key="{x:Static SystemColors.ControlBrushKey}" EndPoint="0,1" StartPoint="0,0">
<GradientStop Color="#FFEEEDED" Offset="0"/>
<GradientStop Color="#FFDDDDDD" Offset="1"/>
</LinearGradientBrush>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Black" />
<SolidColorBrush x:Key="{x:Static SystemColors.ControlTextBrushKey}" Color="Black" />
</TreeView.Resources>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="BorderThickness" Value="1.5"/>
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="BorderBrush" Value="#adc6e5"/>
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="True"/>
<Condition Property="IsSelectionActive" Value="False"/>
</MultiTrigger.Conditions>
<Setter Property="BorderBrush" Value="LightGray"/>
</MultiTrigger>
</Style.Triggers>
<Style.Resources>
<Style TargetType="Border">
<Setter Property="CornerRadius" Value="2"/>
</Style>
</Style.Resources>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>