Selected item customization in ListView

The SfListView supports customizing the selection background color for the selected items by using the SfListView.SelectedItemTemplate if the background color is set to view loaded in the SfListView.ItemTemplate.

<ContentPage  xmlns:syncfusion="clr-namespace:Syncfusion.ListView.XForms;assembly=Syncfusion.SfListView.XForms">
  <syncfusion:SfListView x:Name="listView">
   <syncfusion:SfListView.SelectedItemTemplate>
    <DataTemplate>
     <Grid x:Name="grid" BackgroundColor="RoyalBlue">
      <Grid.RowDefinitions>
         <RowDefinition Height="*" />
         <RowDefinition Height="*" />
         <RowDefinition Height="1" />
       </Grid.RowDefinitions>
      <Label Text="{Binding SongTitle}" />
      <Label Text="{Binding SongAuther}" Grid.Row="1"/>
      <Frame Grid.Row="2" HasShadow="True" HeightRequest="1"/>
     </Grid>
    </DataTemplate>
   </syncfusion:SfListView.SelectedItemTemplate>
  </syncfusion:SfListView>
</ContentPage>

To know more about selection in ListView, please refer our documentationhere.