Can't edit header color

Good day.

I am unable to change my header background color. I currently have the ‘header base dark’ header template inserted, the background still remains white/transparent. Even when changing to other headers and trying to change the background color of any of the rows (top, main, bottom) nothing seems to work as the header remains white.

I thought it might be caused because I had another theme installed prior. But I have disabled all plugins as well as clearing cache as well as other data. Nothing seems to work. Please assist.