Question

 <Grid>
        <ItemsControl ItemsSource="{Binding ScreenViewModelCollection}">
            <ItemsControl.Resources>
                <DataTemplate DataType="{x:Type redScreenView:RedScreenView}">
                    <Grid>
                        <redScreenView:RedScreenView/>
                    </Grid>
                </DataTemplate>

                <DataTemplate DataType="{x:Type greenScreenView:GreenScreenView}">
                    <Grid>
                        <greenScreenView:GreenScreenView/>
                    </Grid>
                </DataTemplate>

            </ItemsControl.Resources>
        </ItemsControl>

Instead of drawing the View for its ViewModel, it prints the namespace that the View belongs to!
But using an ItemTemplate works for just one of them. And ItemTemplate can’t have more than one content 🙁

Answer 1

Your DataTemplates are for Views while I suspect your ScreenViewModelCollection contains ViewModels.

You just need to make the DataType properties be ViewModels instead of Views

<DataTemplate DataType="{x:Type myViewModels:RedScreenViewModel}">
    <Grid>
        <redScreenView:RedScreenView/>
    </Grid>
</DataTemplate>

<DataTemplate DataType="{x:Type myViewModels:GreenScreenViewModel}">
    <Grid>
        <greenScreenView:GreenScreenView/>
    </Grid>
</DataTemplate>