How to change revolution slider background color opacity

.rev_slider .slotholder:after {
	width: 100%;
	height: 100%;
	content: "";
	position: absolute;
	left: 0;
	top: 0;
	pointer-events: none;
	background: rgba(255, 255, 255, 0.5);
}

Can do the same for section background image, just need to add a class to the container and put the .classname in place of .rev_slider .slotholder