NewAuthAndCaptcha/AuthAndCaptcha/Styles.axaml

<Styles xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
  <Design.PreviewWith>
    <Border Padding="20">
      <!-- Add Controls for Previewer Here -->
    </Border>
  </Design.PreviewWith>

	<Style Selector="StackPanel.authSP">
		<Setter Property="Orientation" Value="Vertical"/>
		<Setter Property="HorizontalAlignment" Value="Center"/>
		<Setter Property="Margin" Value="10"/>
	</Style>

	<Style Selector="StackPanel.loginPasswordSP">
		<Setter Property="Orientation" Value="Vertical"/>
		<Setter Property="HorizontalAlignment" Value="Center"/>
	</Style>

	<Style Selector="TextBlock.authMainTitle">
		<Setter Property="FontSize" Value="22"/>
	</Style>

	<Style Selector="StackPanel.loginPasswordT">
		<Setter Property="Margin" Value="8"/>
	</Style>

	<Style Selector="TextBox.authTB">
		<Setter Property="Width" Value="300"/>
		<Setter Property="Height" Value="37"/>
		<Setter Property="BorderBrush" Value="#32CD32"/>
		<Setter Property="Background" Value="#F5F5F5"/>
	</Style>

	<Style Selector="Button.authBut">
		<Setter Property="Background" Value="#32CD32"/>
		<Setter Property="Foreground" Value="White"/>
	</Style>
</Styles>