You can find the ListViewItem styles at templates by editing the template in the designer or by looking them up in the
ListViewItem styles and templates documentation.
This will reveal the following dark theme brushes (light theme has the same names, but different values) which can be overridden in App.xaml:
x:String x:Key="AppName">My App</x:String>
<ResourceDictionary.ThemeDictionaries>
<ResourceDictionary x:Key="Default">
<SolidColorBrush x:Key="ListViewItemSelectedBackgroundThemeBrush" Color="Yellow" />
<SolidColorBrush x:Key="ListViewItemSelectedForegroundThemeBrush" Color="Black" />
</ResourceDictionary>
<ResourceDictionary x:Key="HighContrast">
<SolidColorBrush x:Key="ListViewItemSelectedBackgroundThemeBrush" Color="{ThemeResource SystemColorHighlightColor}" />
<SolidColorBrush x:Key="ListViewItemSelectedForegroundThemeBrush" Color="{ThemeResource SystemColorHighlightTextColor}" />
</ResourceDictionary>
</ResourceDictionary.ThemeDictionaries>
</ResourceDictionary>
</Application.Resources>
You will want to make sure that you override both the foreground and background to ensure that they match and you don't end up with yellow on white, and that you override in normal modes but still provide appropriate high contrast colors for users who need
high contrast mode.
--Rob
