JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
  <div>block1</div>
  <div>block2</div>
  <div class="child">block3</div>
  <div>block4</div>
  <div class="child">block5</div>
  <div>block6</div>
  <div class="child">block7</div>
</div>

JavaScript

$(function(){
$("div.parent div.child:odd").css("background-color", "#F00");
$("div.parent div.child:even").css("background-color", "#00F");

});