Sorry Ruco but I do not have this in my menu… I checked on Customizer > Styling menu and no opacity features… Can you have a direct look as it turns in circle here…
Sorry for my late reply too but it does not change nothing even if I play on hexacolor code replacing the #161616 by #a8a8a8 and ot the opacity (from 0.1 to 0.9).
Ok, found it. In Page menu, on my Home page, at the bottom, the setting Header Over Content was setup as default. I switched it to Transparent header and it works fine!
