Rename the Color singleton to avoid the Qt 6.12 clash

shell/Ui/Toggle.qml

@@ -28,8 +28,8 @@ BorderSurface {
   // Override per-instance if a caller wants the opposite.
   property bool rounded: Style.cornerRadius > 0
 
-  property color foreground: Color.foreground
-  property color accent: Color.accent
+  property color foreground: Colors.foreground
+  property color accent: Colors.accent
   property string fontFamily: Style.font.family
   property real titleSize: Style.font.subtitle
   property real descriptionSize: Style.font.caption