jquery onclick drop down menu with text color change - Need Help!

jquery onclick drop down menu with text color change - Need Help!

Hello.  I am a beginner with jscript and jquery. 

I need your help to find the error in jquery.  I would greatly appreciate if you could validate and tell me what is wrong with my jquery.  Please find the following pasted codes.

I am working on this site(it is in Japanese):

My objective is to make the text color of the top navigational bar gets changed when user click on it(the  2nd one from the left).  Now my jquery is successfully changed the color when the link is clicked.  But I want to stay the text color changed.  Also the first function for dropdown menu has stopped working...!! I want both functions work.  

$(function () {
  $('span').click(function() {
    // menu dropdown 
    $(this).next('ul').slideToggle('fast');
  });  
   // parent link color changes when being clicked
  $('span').click(function() {
    $(this).data('span').changeColor('orange');  
  });
  
 // Positioning of mouse cursor(in / out)
  $('span,ul').hover(function(){
    over_flg = true;
  }, function(){
    over_flg = false;
  });
  
  // closing menu tabs when user clicked outside area
  $('body').click(function() {
    if (over_flg == false) {
      $('ul').slideUp('fast');
    }
  });
});
</script>

From lumierece