firefox-gnome-theme/theme/colors/dark-maia.css

@namespace xul url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

/* Variables that start with --gnome- are added by me and are assigned
 * to elements somewhere in this code. The rest of the variables are
 * built-in in Firefox, so you need to add an !important if you wanna
 * override them. */
@media (prefers-color-scheme: dark) {
	:root {
	  /* Accent */
		--gnome-accent-bg: #16A085;
		--gnome-accent: #16A085;
	}
}