<div class="container">
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
  <div class="item"></div>
</div>

.container {
  display: flex;
  justify-content: center;
  .item {
    width: 150px;
    height: 150px;
    background: blue;
    margin: 10px;
    
    &:nth-child(1) {
      background: blue;
    }
    &:nth-child(2) {
      background: red;
    }
    &:nth-child(3) {
      background: pink;
    }
    &:nth-child(4) {
      background: orange;
    }
  }
}