App.xaml

<Application xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:MauiMultiWindow"
             x:Class="MauiMultiWindow.App">
    <Application.Resources>
        <ResourceDictionary>

            <Color x:Key="PrimaryColor">#512bdf</Color>
            <Color x:Key="SecondaryColor">White</Color>

            <Style TargetType="Label">
                <Setter Property="TextColor" Value="{DynamicResource PrimaryColor}" />
                
            </Style>

            <Style TargetType="Button">
                <Setter Property="TextColor" Value="{DynamicResource SecondaryColor}" />
                
                <Setter Property="BackgroundColor" Value="{DynamicResource PrimaryColor}" />
                <Setter Property="Padding" Value="14,10" />
            </Style>

        </ResourceDictionary>
    </Application.Resources>
</Application>