.box {
  width: 50px;
  height: 50px;
}

.container {
  display: flex;
}

.first.box {
  background-color: hsl(340deg 100% 50% / 1);
}
.second.box {
  background-color: hsl(340deg 100% 50% / 0.75);
}
.third.box {
  background-color: hsl(340deg 100% 50% / 0.5);
}
.fourth.box {
  background-color: hsl(340deg 100% 50% / 0.25);
}