Rename the Color singleton to avoid the Qt 6.12 clash

shell/plugins/panels/quick-settings/PerformanceTab.qml

@@ -101,7 +101,7 @@ Column {
     visible: stats.loadAverage !== ""
     text: "Load average  " + stats.loadAverage
     textFormat: Text.PlainText
-    color: Util.alpha(Color.foreground, 0.7)
+    color: Util.alpha(Colors.foreground, 0.7)
     font.family: Style.font.family
     font.pixelSize: Style.font.bodySmall
   }