JSFiddle - React, Tailwind, and code Playground

HTML

<div class="someGroup">
    <div class="col-md-6">
        <div class="col-md-3 item"></div>
        <div class="col-md-3 item"></div>
        <div class="col-md-3 item"></div>
        <div class="col-md-3 item"></div>
    </div>

    <div class="col-md-6">
        <div class="col-md-3 item"></div>
        <div class="col-md-3 item"></div>
        <div class="col-md-3 item"></div>
        <div class="col-md-3 item"></div> <!-- I want to target this div -->
    </div>
</div>

CSS

.col-md-6
{
    clear:left;
}

.item
{
    float:left;
    width:50px;
    height:50px;
    background:blue;
    margin:2px;
}

.someGroup .col-md-6:last-child .item:last-child {
    background:red;
}