Изменил все

App.xaml

@@ -4,6 +4,10 @@
              xmlns:local="clr-namespace:WPF"
              StartupUri="MainWindow.xaml">
     <Application.Resources>
-         
+        <ResourceDictionary>
+            <ResourceDictionary.MergedDictionaries>
+                <ResourceDictionary Source="Dictionary1.xaml"/>
+            </ResourceDictionary.MergedDictionaries>
+        </ResourceDictionary>
     </Application.Resources>
 </Application>

Dictionary1.xaml

@@ -0,0 +1,9 @@
+<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+                    xmlns:local="clr-namespace:WPF">
+    <Style TargetType="{x:Type Label}">
+        <Setter Property="Background" Value="AntiqueWhite"/>
+        <Setter Property="Padding" Value="0"/>
+    </Style>
+    
+</ResourceDictionary>

WPF.csproj

@@ -55,6 +55,10 @@
       <Generator>MSBuild:Compile</Generator>
       <SubType>Designer</SubType>
     </ApplicationDefinition>
+    <Page Include="Dictionary1.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="MainWindow.xaml">
       <Generator>MSBuild:Compile</Generator>
       <SubType>Designer</SubType>