Ensures Border BorderBrush and Background loading with the right colors.

src/Design.cs

@@ -782,6 +782,26 @@ private IEnumerable<Property> LoadDesignableProperties()
         }
     }
 
+    private Color GetBorderBorderBrush()
+    {
+        if (this.View.Border.BorderBrush == (Color)(-1) && this.View.Border.Parent.ColorScheme != null)
+        {
+            return this.View.Border.Parent.ColorScheme.Normal.Foreground;
+        }
+
+        return this.View.Border.BorderBrush;
+    }
+
+    private Color GetBorderBackground()
+    {
+        if (this.View.Border.Background == (Color)(-1) && this.View.Border.Parent.ColorScheme != null)
+        {
+            return this.View.Border.Parent.ColorScheme.Normal.Background;
+        }
+
+        return this.View.Border.Background;
+    }
+
     private bool ShowTextProperty()
     {
         // never show Text for root because it's almost certainly a container
@@ -796,6 +816,16 @@ private bool ShowTextProperty()
 
     private Property CreateSubProperty(string name, string subObjectName, object subObject)
     {
+        if (name == "BorderBrush")
+        {
+            this.View.Border.BorderBrush = this.GetBorderBorderBrush();
+        }
+
+        if (name == "Background")
+        {
+            this.View.Border.Background = this.GetBorderBackground();
+        }
+
         return new Property(
             this,
             subObject.GetType().GetProperty(name) ?? throw new Exception($"Could not find expected Property '{name}' on Sub Object of Type '{subObject.GetType()}'"),