Color in custom MaterialEntryRenderer - xamarin.forms

Question

Why this line
Control.BackgroundTintList = ColorStateList.ValueOf(Android.Graphics.Color.Green);
is working in a custom EntryRenderer in Android (xamarin forms) and not in a custom MaterialEntryRenderer?
I want to change only the underline color of the entry in material and not the underline color and the placeholder text color too.
xaml
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="Genesys.App.Views.ConfigurationView"
xmlns:local1="clr-namespace:Genesys.App.CustomControls"
Title="Ingrese Configuración"
Visual="Material">
<ContentPage.Content>
<StackLayout VerticalOptions="FillAndExpand"
HorizontalOptions="FillAndExpand"
Padding="15"
Background="white">
<local1:MyEntry x:Name="txtServicio"
Placeholder="SERVICIO"
BackgroundColor="White">
</local1:MyEntry>
<Button Padding="5"
Margin="5"
Text="guardar"
TextTransform="Uppercase"
TextColor="white"
BackgroundColor="{StaticResource colorPrimary}"
HorizontalOptions="End"
Command="{Binding ButtonCommand}"></Button>
</StackLayout>
</ContentPage.Content>
</ContentPage>
//class MyEntry
public class MyEntry : Entry
{
}
CustomEntryRenderer in android
[assembly: ExportRenderer(typeof(MyEntry), typeof(MyRenderer))]
namespace Genesys.App.Droid
{
public class MyRenderer : EntryRenderer//this works
{
public MyRenderer(Context context) : base(context)
{
}
protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
{
base.OnElementChanged(e);
if (Control != null)
{
this.EditText.FocusChange += (sender, ee) => {
bool hasFocus = ee.HasFocus;
if (hasFocus)
{
Control.BackgroundTintList = ColorStateList.ValueOf(Android.Graphics.Color.Green); //changes color
}
else
{
Control.BackgroundTintList = ColorStateList.ValueOf(Android.Graphics.Color.Red); //changes color
}
};
}
}
}
}
//don't work
[assembly: ExportRenderer(typeof(MyEntry), typeof(MyRenderer))]
namespace Genesys.App.Droid
{
public class MyRenderer : MaterialEntryRenderer//don't work
{
public MyRenderer(Context context) : base(context)
{
}
protected override void OnElementChanged(ElementChangedEventArgs<Entry> e)
{
base.OnElementChanged(e);
if (Control != null)
{
this.EditText.FocusChange += (sender, ee) => {
bool hasFocus = ee.HasFocus;
if (hasFocus)
{
Control.BackgroundTintList = ColorStateList.ValueOf(Android.Graphics.Color.Green);//doesn't change color
}
else
{
Control.BackgroundTintList = ColorStateList.ValueOf(Android.Graphics.Color.Red); //doesn't change color
}
};
}
}
}
}