Hello,

You have to set the font color into Specular > Header Options > Default Page Header > Change font color https://imgur.com/S03US84 set it white.

Also edit the file header.php file and replace this codes:

if(isset($page_header_menu_color) && !empty($page_header_menu_color))
            $bgCheck = ($page_header_menu_color =='auto') ? '' : 'background--'.$page_header_menu_color; 
        else
            $bgCheck = 'background--light';
    } 

replace with:

if(isset($page_header_menu_color) && !empty($page_header_menu_color))
            $bgCheck = ($page_header_menu_color =='auto') ? '' : 'background--dark'; 
        else
            $bgCheck = 'background--dark';
    } 

Save the file and replace any time if you will get a new update or create a child theme.

Let us know.

Regards!