Overlay

overlay.css

.overlay{
  position: relative;
}

.overlay > *{
  position: relative;
  z-index: 1;
}

.overlay:before{
  content: '';
  position: absolute;
  height: 100%;
  width: 100%;
  opacity: 0.3;
  z-index: 0;
}

.overlay.dark:before{
  background-color: #000;
  color: #fff;
}

.overlay.dark{
  color: #fff;
}

.overlay.light:before{
  background-color: #fff;
}

.overlay.light{
  color: #000;
}