小编beg*_*ner的帖子

.blackBox {
  background: #000;
  z-index: 0;
}

.text {
  color: #000;
  z-index: 2;
}

.redBox {
  background: red;
  opacity: 0.5;
  z-index: 1;
}

<div class="blackBox">
  <div class="text">Lorem Ipsum Neque porro quisquam est qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit... </div>
  <div class="redBox" />
</div>