https://git.xfce.org/xfce/xfdesktop/tree/settings/xfdesktop-settings-appearance-frame-ui.glade#n229 <property name="rgba"/> This line was added by https://git.xfce.org/xfce/xfdesktop/commit/settings/xfdesktop-settings-appearance-frame-ui.glade?id=1a4525c9e9605825d318414cceb3ccb085cd7795 and triggers the following Gtk warning when the user opens xfdesktop-settings: Failed to set property GtkColorButton.rgba to : Could not not parse RGBA color ''
Andre Miranda referenced this bugreport in commit 4c53c9275219bd48c76793cc6b2f8b90bb0787f9 Remove faulty line in glade file (Bug #15293) https://git.xfce.org/xfce/xfdesktop/commit?id=4c53c9275219bd48c76793cc6b2f8b90bb0787f9
Good catch, thanks for pointing this out.