App.xaml

<Application x:Class="WPF_Utils.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:WPF_Utils"
             xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <materialDesign:BundledTheme BaseTheme="Light" PrimaryColor="DeepPurple" SecondaryColor="Purple" />
                <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesign3.Defaults.xaml" />
            </ResourceDictionary.MergedDictionaries>

            <SolidColorBrush x:Key="AppBackground" Color="#FFF5F3F8" />
            <SolidColorBrush x:Key="SidebarBackground" Color="#FFEBE6F0" />
            <SolidColorBrush x:Key="AppText" Color="#FF333333" />
        </ResourceDictionary>
    </Application.Resources>
</Application>