Demo: CSS mask-composite

<div class='container'>
  <div class='mask1'></div>
  <div class='mask2'></div>
</div>

.container {
  position: relative;
  width: 200px;
  height: 200px;
  background-color: lightblue;
  overflow: hidden;
}

.mask1 {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(255, 0, 0, 0.5);
  -webkit-mask-image: radial-gradient(circle, black 50%, transparent 51%);
  mask-image: radial-gradient(circle, black 50%, transparent 51%);
}

.mask2 {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 255, 0.5);
  -webkit-mask-image: radial-gradient(circle, black 50%, transparent 51%);
  mask-image: radial-gradient(circle, black 50%, transparent 51%);
  mask-composite: exclude;
}

// No JavaScript required for this demo