myentrymaincustomized.xaml

<...
             xmlns:local="clr-namespace:EntryAccent"
             x:Class="EntryAccent.MainPage"
             >
    ...
            <local:MyEntry Text="Text" TextColor="White" PlaceholderColor="Green" BackgroundColor="YellowGreen" MyHighlightColor="Blue" MyHandleColor="Violet" MyTintColor="Black" />
            <local:MyEntry Placeholder="Placeholder" TextColor="White" PlaceholderColor="Green" BackgroundColor="YellowGreen" MyHighlightColor="Blue" MyHandleColor="Violet" MyTintColor="Black" />
    ...