I can’t figure out how to do the transparent red highlight on the header

Thanks

Some of the features of this specific custom header is achieved with custom CSS (for presentation purposes). You can see it once you edit that page (if you imported the DEMO) and click on the Settings icon (top right) in order to see the custom CSS that applies for this specific page.

Other than that via Theme options you can customize the transparent header background/transparency as well as the navigation color of the transparent header, also the sticky header text color etc. Get what you can via the theme options, we can help you with the rest if you know what you are after.

Do you want this transparent/sticky header globally or just on this specific page?
I added the custom styles to that page, you can see them when you click the CSS button (top right in the editor)… you don’t need all of them obviously if you are not to use the sticky header.