App.xaml

<Application x:Class="euroPlus4_1.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml">
    
    <Application.Resources>
        
        <ResourceDictionary>
            <SolidColorBrush x:Key="MahApps.Brushes.ToggleSwitch.Control.BorderBrushProperty" Color="Blue" />
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
                <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Themes/Light.Blue.xaml" />
                
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>