<ol>
  <li>Ruby</li>
  <li>Python</li>
  <li>JavaScript</li>
  <li>Go</li>
  <li>PHP</li>
  <li>Scala</li>
  <li>Java</li>
  <li>Kotlin</li>
  <li>C++</li>
  <li>C</li>
  <li>Cobol</li>
  <li>Fortran</li>
</ol>
ol {
  color: gray;
}

ol :nth-child(3n+1) {
  color: red;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.