Rename the Color singleton to avoid the Qt 6.12 clash

shell/plugins/bar/widgets/ActiveWindow.qml

@@ -34,7 +34,7 @@ BarWidget {
       anchors.left: parent.left
       width: parent.width
       text: root.title
-      color: root.bar ? root.bar.barForeground : Color.foreground
+      color: root.bar ? root.bar.barForeground : Colors.foreground
       font.family: root.bar ? root.bar.fontFamily : Style.font.family
       font.pixelSize: Style.font.body
       elide: Text.ElideRight