Blog Post
Introducing new SharePoint Site Header & Footer Enhancements
It is currently not possible to have a navigation bar with the theme color in the extended header, as it was before, for better readability. Do you plan to enable the option to leave the navigation bar transparent or set it as opaque if I have an extended header set? It is currently quite impractical and will make it impossible to use the header to display various images as a banner, since it is not possible to set a full-width banner with its own image height in the body of the page. The opacity of the navigation cannot be treated graphically either, because the display is dynamic. In my opinion, you should leave the admin the option to decide whether he wants the navigation to be transparent or solid color for the readability of the buttons. Thanks for the answer.