ul#principal {
	border: 1px solid red;
	width: 200px;
	background-color: #aaaaaa;

	li {
		color: red;
		
		a {
			color: black;
		}
	}
	li.on {
		background-color: red;
		color: white;
		
		a {
			color: #ffaaaa;
		}
	}
}