JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="postcontainer">
        <div class="latest-posts">
            <div class="thumbnail"></div>
            <div class="pcontain"></div>
            <div class="more"></div>
        </div>
    </div>
    <div class="postcontainer">
        <div class="latest-posts">
            <div class="thumbnail"></div>
            <div class="pcontain"></div>
            <div class="more"></div>
        </div>
    </div>
    <div class="postcontainer">
        <div class="latest-posts">
            <div class="thumbnail"></div>
            <div class="pcontain"></div>
            <div class="more"></div>
        </div>
    </div>
    <div class="postcontainer">
        <div class="latest-posts">
            <div class="thumbnail"></div>
            <div class="pcontain"></div>
            <div class="more"></div>
        </div>
    </div>
</div>

CSS

.pcontain{
    
    background: red;
    color: white;
    width: 100px;
    height: 30px;
    margin-bottom: 5px;
}

.postcontainer:last-child .pcontain{ 
    background: black;
    color: white;
}