MobileApps-What does the coloring mean on the list of event?

$(".header").click(function () {

   $header = $(this);
   //getting the next element
   $content = $header.next();
   //open up the content needed - toggle the slide- if visible, slide up, if not slidedown.
   $content.slideToggle(500, function () {
       //execute this after slideToggle is done
       //change text of header based on visibility of content div
       $header.text(function () {
           //change text based on condition
           return $content.is(":visible") ? "Collapse" : "Expand";
       });
   });

});

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• This is just some random content.
• This is just some random content.
• This is just some random content.
• This is just some random content.