MSW specific: Fixed update of the UI after system color change.

Note: the wxEVT_SYS_COLOUR_CHANGED event works only for high contrast settings under MSW.

+ ConfigSnapshotDialog: Fixed UI colors for dark mode on all platforms

src/slic3r/GUI/Preferences.cpp

@@ -51,6 +51,9 @@ void PreferencesDialog::build()
 	auto app_config = get_app_config();
 
 	wxNotebook* tabs = new wxNotebook(this, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxNB_TOP | wxTAB_TRAVERSAL | wxNB_NOPAGETHEME);
+#ifdef __WXMSW__
+    tabs->SetBackgroundColour(wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW));
+#endif
 
 	// Add "General" tab
 	m_optgroup_general = create_options_tab(_L("General"), tabs);