JSFiddle - React, Tailwind, and code Playground

HTML

<div id="prop-images-wrapper">
  <ul>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_1.jpg" width="134" height="102" alt="Property thumb"></li>
    <li class="property-thumbnail"><img src="http://s3.amazonaws.com/assets.indagare.com/photos/0009/2598/LeBlue_Villa_b_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:nth-child(2n+1), .difcolor {
    margin-right: 0px;
    background-color: #06F;
}

JavaScript

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