JSFiddle - React, Tailwind, and code Playground

HTML

<section class="form-block">
        <div class="form-group has-errors">
              ERROR!
        </div>
        <div class="form-group has-errors">
              ERROR!
        </div>
        <div class="form-group">
              stuff
        </div>
    </section>

CSS

.form-block .form-group.has-errors:last-child {
      background-color: blue;
    }