testsuite/css/style/adjacent-states.css - external/github.com/GNOME/gtk - Git at Google

 checkbutton:checked + label {
   color: red;
 }

 checkbutton + label {
   color: blue;
 }
	checkbutton:checked + label {
	color: red;
	}

	checkbutton + label {
	color: blue;
	}