How to change StackLayout background color inside a ListView

Hi! Thanks for reading this.
I'm trying to change StackLayout Background Color for some items inside a ListView. I use this background color for some special items inside de listview.
Here's my xaml.

    <ListView x:Name="lst" ItemsSource="{Binding ListSource}"  ItemSelected="lst_ItemSelected" >
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell>
                    <ViewCell.View>
                        <StackLayout x:Name="Back" Padding="10" Margin="10"  BackgroundColor="{Binding BackgroundColor}" Orientation="Horizontal">
                            <Label Text="{Binding Texto}" TextColor="White" />
                        </StackLayout>
                    </ViewCell.View>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

ListSource model has a BackColor property, so, some items have Gray background color, and others just keep transparent.
When an item is selected , there is no problem with transparent ones, but red replaces selected color.

So, I would like when one item was selected, if it has a gray background color then it must to change to transparent, and return to gray when lost selection.

I have been try with a ContentView , for extract DataTemplate to another xaml getting access to StackLayout, and tried a lot of examples that I found on internet. Nothing worked.

Thanks in advance.
Gaston.