Edit in JSFiddle

body {
    var-green: #bada55;
}		
.foo {
		    background: var(green);
		}
		.bar {
		    background: black;
		    color: var(green);
		}
		.fizz {
		    background: rgba(0, 0, 0, 0.5);
		    color: var(green);
		}
		.buzz {
		    background: var(green);
		    color: white;
		}