Fix

src/ThemeEditor.Controls.ColorPicker/ColorPicker.axaml

@@ -225,7 +225,7 @@
     <Setter Property="ClipValueToMinMax" Value="True" />
     <Setter Property="ShowButtonSpinner" Value="True" />
     <Setter Property="AllowSpin" Value="True" />
-    <Setter Property="CultureInfo" Value="en-US" />
+    <Setter Property="NumberFormat" Value="{x:Static cp:ColorPicker.NumberFormat}" />
     <Setter Property="Margin" Value="2" />
     <Setter Property="Padding" Value="1" />
   </Style>

src/ThemeEditor.Controls.ColorPicker/ColorPicker.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Globalization;
 using System.Reactive.Disposables;
 using Avalonia;
 using Avalonia.Collections;
@@ -12,6 +13,8 @@ namespace ThemeEditor.Controls.ColorPicker;
 
 public class ColorPicker : TemplatedControl
 {
+    public static readonly NumberFormatInfo NumberFormat = new CultureInfo("en-US").NumberFormat;
+
     public static readonly StyledProperty<Color?> ColorProperty =
         AvaloniaProperty.Register<ColorPicker, Color?>(nameof(Color));