JSFiddle - React, Tailwind, and code Playground

HTML

<select class="box_length" id="alert_type" onchange="this.className=this.options[this.selectedIndex].className">
  <option value="Value1" class="Value1">Value1</option>
  <option value="Value2" class="Value2">Value2</option>
  <option value="Value3" class="Value3">Value3</option>
  <option value="Value4" class="Value4">Value4</option>
</select>

CSS

.Value1 {
  background-color: #006600;
  color: white;
}

.Value2 {
  background-color: #000080;
  color: white;
}

.Value3 {
  background-color: #e6e600;
}

.Value4 {
  background-color: #660066;
  color: white;
}