JSFiddle - React, Tailwind, and code Playground

HTML

<div class="ui-select-container ui-select-bootstrap dropdown ng-valid ng-touched ng-dirty ng-valid-parse">
  <div class="ui-select-match">
    <span class="btn btn-default form-control ui-select-toggle">test</span>
  </div>
</div>

CSS

.ui-select-container.ui-select-bootstrap.dropdown.ng-valid.ng-touched.ng-dirty.ng-valid-parse > .ui-select-match > span {
    width: 60%;
    background-color: #000;
    color: #fff;
}