Consider documenting pkgdown-navbar-bg and pkgdown-navbar-bg-dark as needed to set navbar color with a bootswatch theme with light-switch enabled

[remlapmot]

I contribute to a site on which we've traditionally used the United theme https://bootswatch.com/united/. That theme uses a navbar in Ubuntu orange.

In pkgdown 2.1.0 if I don't specify the light-switch the navbar is the expected colour (as it is when using previous versions of pkgdown).

But if I enable the light-switch the navbar is set to a much lighter colour than that defined in the theme.

Looking at the code

pkgdown/inst/BS5/assets/pkgdown.scss

Lines 23 to 40 in f20a649

	$pkgdown-navbar-bg: null !default;
	$pkgdown-navbar-bg-dark: null !default;
	// BS navbars appears to be designed with the idea that you have a coloured
	// navbar that looks the same in both light and dark mode. We prefer a mildly
	// coloured navbar that's just different enough from the body to stand out.
	//
	// Relies on CSS fallback rules
	.navbar {
	background: RGBA(var(--bs-body-color-rgb), 0.1);
	background: color-mix(in oklab, color-mix(in oklab, var(--bs-body-bg) 95%, var(--bs-primary)) 95%, var(--bs-body-color));
	background: $pkgdown-navbar-bg;
	// Harmonize alignment of navbar elements (search field vs. rest)
	line-height: initial;
	}
	[data-bs-theme="dark"] .navbar {
	background: $pkgdown-navbar-bg-dark;
	}

I think you've kindly left an override in, pkgdown-navbar-bg (and pkgdown-navbar-bg-dark), which I used to specify the expected navbar colour under the bslib menu, but these don't seem to be documented.

template:
  bootstrap: 5
  light-switch: true
  bslib:
    bootswatch: united
    pkgdown-navbar-bg: '#e95420'

With this specified I get the expected navbar color.

These two variables are certainly helpful to me and would seem worth a mention in the customise.Rmd vignette.

[certara-mtalley]

Encountered the same issue with the same color. This tip was greatly appreciated!