Hi I check it and this what you have to do, in you joomla go to template and in the files find this template/gk-news2/css/template css
I think you have a folder with this name template css in the left side you have a number find this number 738 in that line you have this code
and you have to change this:
je_accord754.je_acc > ul > li > a:hover, #je_accord754.je_acc > ul > li.active > a, #je_accord754.je_acc > ul > li.open > a { template css:738
color: #f08937 !important;
background: none !important;
change this:
color: #f08937 !important;.... for this.... background-color: #f08937 !important;
and delete this: background: none !important;
on your website in that menu click on what you want to change color, then click the right button and select inspect, reviews the code, in your right side is where are the css and there you can change color so you can see which is the one who does that change.
when you have it, look up, there is a league where it indicates the folder, go to your template and searches that folder and there you can change it. Also in that league you can see the number of that code