diff --git a/CotEditor/Sources/DocumentWindow.swift b/CotEditor/Sources/DocumentWindow.swift
index f9852a8278..920466fd68 100644
--- a/CotEditor/Sources/DocumentWindow.swift
+++ b/CotEditor/Sources/DocumentWindow.swift
@@ -24,7 +24,6 @@
 //
 
 import AppKit
-import Combine
 
 final class DocumentWindow: NSWindow {
     
@@ -59,11 +58,6 @@ final class DocumentWindow: NSWindow {
     }
     
     
-    // MARK: Private Properties
-    
-    private var appearanceObserver: AnyCancellable?
-    
-    
     
     // MARK: -
     // MARK: Window Methods
@@ -98,17 +92,6 @@ final class DocumentWindow: NSWindow {
         
         didSet {
             self.didChangeValue(for: \.isOpaque)
-            
-            guard isOpaque != oldValue else { return }
-            
-            self.invalidateTitlebarOpacity()
-            
-            if isOpaque {
-                self.appearanceObserver = nil
-            } else if self.appearanceObserver == nil {
-                self.appearanceObserver = self.publisher(for: \.effectiveAppearance)
-                    .sink { [weak self] _ in self?.invalidateTitlebarOpacity() }
-            }
         }
     }
     
@@ -172,17 +155,6 @@ final class DocumentWindow: NSWindow {
             self.invalidateRestorableState()
         }
     }
-    
-    
-    /// Make sure window title bar (incl. toolbar) is opaque.
-    private func invalidateTitlebarOpacity() {
-        
-        guard let titlebarView = self.standardWindowButton(.closeButton)?.superview else { return }
-        
-        // dirty manipulation to avoid the title bar being dyed in the window background color (2016-01).
-        titlebarView.wantsLayer = !self.isOpaque
-        titlebarView.layer?.backgroundColor = self.isOpaque ? nil : NSColor.windowBackgroundColor.cgColor(for: self.effectiveAppearance)
-    }
 }
 
 
diff --git a/CotEditor/Sources/HoleContentView.swift b/CotEditor/Sources/HoleContentView.swift
index 79279d6b25..217e0021fd 100644
--- a/CotEditor/Sources/HoleContentView.swift
+++ b/CotEditor/Sources/HoleContentView.swift
@@ -43,7 +43,7 @@ final class HoleContentView: NSView {
         
         super.viewWillMove(toWindow: newWindow)
         
-        self.windowOpacityObserver = newWindow?.publisher(for: \.isOpaque)
+        self.windowOpacityObserver = newWindow?.publisher(for: \.isOpaque, options: .initial)
             .sink { [unowned self] isOpaque in
                 self.holeViewObserver = if isOpaque {
                     nil
diff --git a/CotEditor/Sources/NSColor+NamedColors.swift b/CotEditor/Sources/NSColor+NamedColors.swift
index 3d6caf442e..5a6d5724d6 100644
--- a/CotEditor/Sources/NSColor+NamedColors.swift
+++ b/CotEditor/Sources/NSColor+NamedColors.swift
@@ -35,23 +35,6 @@ extension NSColor {
 
 extension NSColor {
     
-    /// Return CGColor of the receiver by converting system color correctly for the specific appearance.
-    ///
-    /// - Parameter appearance: The appearance to get the corresponding system color.
-    /// - Returns: A CGColor instance.
-    func cgColor(for appearance: NSAppearance) -> CGColor {
-        
-        guard NSAppearance.currentDrawing() != appearance else { return self.cgColor }
-        
-        var cgColor: CGColor = .clear
-        appearance.performAsCurrentDrawingAppearance {
-            cgColor = self.cgColor
-        }
-        
-        return cgColor
-    }
-    
-    
     /// Create desired number of well distributed colors from the receiver.
     ///
     /// - Parameter number: The required number of colors.