Rename the Color singleton to avoid the Qt 6.12 clash

shell/Ui/Panel.qml

@@ -19,7 +19,7 @@ Item {
   property bool popoutSwitchClosing: false
 
   readonly property bool opened: panelController.open
-  readonly property color barForeground: bar ? bar.barForeground : Color.foreground
+  readonly property color barForeground: bar ? bar.barForeground : Colors.foreground
 
   function open() { panelController.show() }
   function close() { panelController.hide() }