Hey guys!
So this was a head scratcher for me. Probably because I set up this nav essentially backwards compared to how it should be done! My Bad! Still…
Problem: You have your menu set to ‘Menu Icon’ across all devices. Your ‘current’ menu item status does not appear and you want to change the current menu item link colour, and you ARE on the current page.
Fix: Switch the ‘menu icon’ off for desktop, (and you may have to switch back to desktop view
at this point if it auto changes your view to tablet)
This will then ‘unlock’ the menu so ‘current’ should then appear on the menu item, and you can then go ahead and style the ‘current’ state.
This is may not be relevant to all you pro’s out there 
but for myself, this is the answer I needed. If it helps anyone else, I’ve passed it on!
Also - set your menu states before you get this far! haha! (ahem) lesson learnt! 