Labels and Entries, by default, have no color in Xamarin.Forms

Question

I have created a Xamarin Android Shell app. All the labels and Entries are in blank color and don't display on the android device until I change it to black or other colors. Below is a code snippet for the login page.

<?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="VaxineApp.Views.Login.LoginPage"
             xmlns:local="clr-namespace:VaxineApp.Renderers"
             Shell.FlyoutBehavior="Disabled"
             Shell.NavBarIsVisible="False">
  <ContentPage.Content>
    <StackLayout Padding="40" VerticalOptions="Center" HorizontalOptions="FillAndExpand"> 
      <Label Text="Welcome to Login Page" />
      <Entry Placeholder="Email or Phone"></Entry>
      <Entry Placeholder="Password"></Entry>
      <Button Text="Sign in"></Button>
    </StackLayout>
  </ContentPage.Content>
</ContentPage>  

I don't know whether I am missing something. That hasn't happened to me before.
See how this code renders on my Android device.