How to change the colour/transparancy on the mobile nav after adding custom code to make navigation drop downs transparent

Site URL: https://sturgeon-fiddle-fxnb.squarespace.com

Hey guys! 

I am struggling with something. I have used a plugin to have nested drop down menus and then adding css to make the background of these menus transparent as we preferred the look. But now, the mobile menu nav is also transparent which makes it impossible to read. 

Any code out there to change the colour of the mobile nav menu back to the background colour without touching the design of the desktop version? 

Thank you! 

Website: https://sturgeon-fiddle-fxnb.squarespace.com

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