Rename the Color singleton to avoid the Qt 6.12 clash

shell/plugins/panels/audio/Panel.qml

@@ -177,10 +177,10 @@ Panel {
   readonly property string toggleHint: anyAudible ? "Mute" : "Unmute"
 
   readonly property color hoverFill: bar
-    ? Style.hoverFillFor(bar.foreground, Color.accent)
+    ? Style.hoverFillFor(bar.foreground, Colors.accent)
     : "transparent"
   readonly property color selectedFill: bar
-    ? Style.selectedFillFor(bar.foreground, Color.accent)
+    ? Style.selectedFillFor(bar.foreground, Colors.accent)
     : "transparent"
 
   function sectionCount(section) {