Module:Calculator widget/style.css

.calculatorwidget {
	background-color: #eee
}

@media screen {
	html.skin-theme-clientpref-night .calculatorwidget {
		background-color: #333;
	}
}

@media screen and (prefers-color-scheme: dark) {
	/* automatic mode */
	html.skin-theme-clientpref-os .calculatorwidget {
		background-color: #333;
	}
}