Address review comments

src/citra_qt/configuration/configure_graphics.cpp

@@ -109,7 +109,7 @@ void ConfigureGraphics::updateShaders(bool anaglyph) {
     }
 }
 
-void ConfigureGraphics::UpdateBackgroundColorButton(QColor color) {
+void ConfigureGraphics::UpdateBackgroundColorButton(const QColor& color) {
     bg_color = color;
 
     QPixmap pixmap(ui->bg_button->size());

src/citra_qt/configuration/configure_graphics.h

@@ -22,7 +22,7 @@ public:
     void RetranslateUI();
     void SetConfiguration();
 
-    void UpdateBackgroundColorButton(QColor color);
+    void UpdateBackgroundColorButton(const QColor& color);
 
     std::unique_ptr<Ui::ConfigureGraphics> ui;
     QColor bg_color;