How to change the iOS navigation's bar background-color

To make a website fullscreen on iOS, add the following to index.html header:

html
<meta name = "viewport" content = "width=device-width, initial-scale = 1, shrink-to-fit = no">

You can change the bar's color behind the URL by setting the theme color (no need to modify the CSS). For example, let's change the background to black:

html
<meta name = "theme-color" content = "#000000">

Or to navy:

html
<meta name = "theme-color" content = "#243b55">

If you remove the theme-color meta tag, iOS will decide the background color (generally it'll use the same color as the one in the body).