Template:Userbox/styles.css

.wikiuserbox-default {
	background-color: #eee;
	color: #000;
}

/* Colours for dark mode GUI */
@media screen {
    html.skin-theme-clientpref-night .wikiuserbox-default {
		background-color: #333;
		color: #fff;
	}
    html.skin-theme-clientpref-night .wikiuserbox-nocolorset {
		background-color: #333;
		color: #fff;
	}
}

@media screen and ( prefers-color-scheme: dark ) {
    html.skin-theme-clientpref-os .wikiuserbox-default {
		background-color: #333;
		color: #fff;
	}
    html.skin-theme-clientpref-os .wikiuserbox-nocolorset {
		background-color: #333;
		color: #fff;
	}
}