resources/themes/Light.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
 
    <SolidColorBrush x:Key="WindowBackground" Color="White"/>
    <SolidColorBrush x:Key="ControlBackground" Color="WhiteSmoke"/>
    <SolidColorBrush x:Key="ControlForeground" Color="Black"/>
    <SolidColorBrush x:Key="ButtonBackground" Color="#E0E0E0"/>
    <SolidColorBrush x:Key="ButtonForeground" Color="Black"/>
 
    <Style TargetType="Control">
        <Setter Property="Background" Value="{DynamicResource ControlBackground}" />
        <Setter Property="Foreground" Value="{DynamicResource ControlForeground}" />
    </Style>
 
    <Style TargetType="Button">
        <Setter Property="Background" Value="{DynamicResource ButtonBackground}" />
        <Setter Property="Foreground" Value="{DynamicResource ButtonForeground}" />
    </Style>
 
    <Style TargetType="Window">
        <Setter Property="Background" Value="{DynamicResource WindowBackground}" />
    </Style>
</ResourceDictionary>