App.xaml

<Application x:Class="Calculator_.NET_Core.App"
            xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
            xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
            xmlns:local="clr-namespace:Calculator_.NET_Core"
            StartupUri="MainWindow.xaml">
    <Application.Resources>

        <SolidColorBrush x:Key="blackColor" Color="Black"/>
        <SolidColorBrush x:Key="whiteColor" Color="GhostWhite"/>
        <SolidColorBrush x:Key="yellowColor" Color="Orange"/>
        <SolidColorBrush x:Key="grayColor" Color="DarkGray"/>

        <Style TargetType="Button" x:Key="numberButtonAttribute">
            <Setter Property="Foreground" Value="{StaticResource whiteColor}"/>
            <Setter Property="Background" Value="{StaticResource blackColor}"/>
            <Setter Property="FontSize" Value="30"/>
        </Style>

        <Style TargetType="Button" x:Key="operatorButtonAttribute" BasedOn="{StaticResource numberButtonAttribute}">
            <Setter Property="Background" Value="{StaticResource yellowColor}"/>
        </Style>

        <Style TargetType="Button" x:Key="additionalButtonAttribute" BasedOn="{StaticResource numberButtonAttribute}">
            <Setter Property="Foreground" Value="{StaticResource blackColor}"/>
            <Setter Property="Background" Value="{StaticResource grayColor}"/>
        </Style>
        
    </Application.Resources>
</Application>