JSFiddle - React, Tailwind, and code Playground

HTML

<div id="prop-images-wrapper">
  <ul>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="img/real-state-for-sale/properties/thumbnails/le-blue-villa-1.jpg" width="134" height="102" alt="Property thumb"></li>
  </ul>
</div>

CSS

#prop-images-wrapper {
float: left;
margin-bottom: 0.6em;
background-color: #F00;
width: 340px;
margin-right: 5px;}

#prop-images-wrapper li.difcolor {
margin-right: 0px;
background-color: #06F;}

JavaScript

$("#prop-images-wrapper li:nth-child(2n+1)").addClass("difcolor");