Hi,
I recently purchased the Jannah theme and am wanting to change the colour of the highlighted menu tab along the bottom of the header. Can someone please help?
You should contact the theme author for support
Why you don’t use css file to change that color with your color?
I would if I even knew what your were talking about? LOL
How do I do that?
Go to themeforest.net/downloads and click on the item name which you have bought. Then comment on their item landing page to contact the author. Hope they will help you as soon as possible. Cheers. 
You can right click and inspect elements you will get css file and css line, you open that css and change color code
Thanks