// Press arrow keys and arrow graphic changes color
$(document.documentElement).keydown(function (event) {

  if (event.keyCode == 37) {
    $('a#prev').addClass('hover');
  
  } else if (event.keyCode == 39) {
    $('a#next').addClass('hover');
  
  }

});

// Release arrow key and slideshow scrolls
$(document.documentElement).keyup(function (event) {

  if (event.keyCode == 37) {
    $('a#prev').click().removeClass('hover');
    
  } else if (event.keyCode == 39) {
    $('a#next').click().removeClass('hover');
  
  }

});