How do I get the title bar to be darker?

[imjamesb]

I cannot get the title bar darker than #595959 as you see in the picture below.

How can I make it the same color as my background? Can't seem to find any good resources on this.

Here's my XAML

<Window
	x:Class="Powertoys.MainWindow"
	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
	xmlns:local="using:Powertoys"
	xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
	
	mc:Ignorable="d">

	<Grid
		Background="#303030">
		<Grid.ColumnDefinitions>
			<ColumnDefinition
				Width="Auto" />
			<ColumnDefinition
				Width="*" />
		</Grid.ColumnDefinitions>
		<Border
			x:Name="AppTitleBar"
			Grid.Column="1"
			VerticalAlignment="Top"
			Background="Transparent"
			BorderThickness="0"
			IsHitTestVisible="True"
			Canvas.ZIndex="1"
>
			<TextBlock
				x:Name="AppTitle"
				Text="{StaticResource AppTitleName}"
				VerticalAlignment="Center"
				TextAlignment="Start"
				Margin="10, 10, 10, 10"
				/>
		</Border>
	</Grid>
</Window>

An my C# code

public sealed partial class MainWindow : Window {
	public MainWindow() {
		this.InitializeComponent();
		this.ExtendsContentIntoTitleBar = true;
		this.SetTitleBar(AppTitleBar);
	}
}

Expected result:

[castorix]

You can change the Opacity like I did in App.xaml in the test sample I had posted (WinUI3_CustomCaption)
For example, with Opacity = "0" and

<Border Background="#000000">

in MainWindow.xaml,
I get a black background :

[brandon3343]

set this to App.xaml

<SolidColorBrush x:Key="WindowCaptionBackground" Color="Transparent" />
<SolidColorBrush x:Key="WindowCaptionBackgroundDisabled" Color="Transparent" />

full code

<Application
    x:Class="monitor_helper.App"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:converters="using:CommunityToolkit.WinUI.UI.Converters"
    xmlns:local="using:monitor_helper">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
                <!--  Other merged dictionaries here  -->
            </ResourceDictionary.MergedDictionaries>
            <!--  Other app resources here  -->
            <SolidColorBrush x:Key="WindowCaptionBackground" Color="Transparent" />
            <SolidColorBrush x:Key="WindowCaptionBackgroundDisabled" Color="Transparent" />
        </ResourceDictionary>
    </Application.Resources>
</Application>

[imjamesb]

I should've suggested an answer a while ago, I inspected the source code from the WinUI 3 gallery and ended up with this: