CodePen

HTML

            
              <div class="wrapper">
  <div class="box"></div>
  <div class="pick-me"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
  <div class="box"></div>
</div>
            
          
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↑ Insert the most common viewport meta tag

CSS

            
              .wrapper {
  max-width:90%;
  margin:25px auto;
  text-align:center;
}

.box, .pick-me {
  width:50px;
  height:50px;
  margin-right:10px;
  display:inline-block;
  background:grey;
}

.pick-me {
  background:green;
}

.box:nth-child(3) {
  background:red;
}

.box:nth-of-type(4) {
  background:blue;
}

div:nth-child(5) {
  background: lightgreen;
}

div:nth-of-type(6) {
  background: #bada55;
}
            
          
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JS

            
              
            
          
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