PP_Minin/PP_Ven_MosS/App.xaml

<Application x:Class="PP_Ven_MosS.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:PP_Ven_MosS"
             StartupUri="MainWindow.xaml">
    <Application.Resources>
        <Style x:Key="GBSt" TargetType="GroupBox">
            <Setter Property="BorderBrush" Value="#FF0000"></Setter> 
            <Setter Property="Width" Value="300"></Setter>
            <Setter Property="BorderThickness" Value="1"></Setter>
        </Style>
        <Style x:Key="BtnSt" TargetType="Button">
            <Setter Property="Background" Value="#FF0000"></Setter>
            <Setter Property="Height" Value="30"></Setter>
            <Setter Property="Width" Value="200"></Setter>
        </Style>
    </Application.Resources>
</Application>