Theme: FullScreen – Changing the Naviagtion Bar Colour

Hello

I am running the FullScreen Theme by GraphPaperPress. It seems pretty straight forward but I can not for the life of me figure out how to change the colour of the navigation bar that runs down the middle of the page.

I have sort of figured out that it is the #branding area that I need to edit. But when I change those values in the CSS editor, nothing happens.

Any help would be appreciated. My website is https://www.amymarkanda.com