JSFiddle - React, Tailwind, and code Playground

HTML

<select class="colab-select" name="colab[]" multiple>
    <option value="1" selected>Dexter</option>
    <option value="2" selected>James</option>
    <option value="3">Mary</option>
    <option value="1">Dexter</option>
    <option value="2">James</option>
    <option value="3">Mary</option>
</select>

JavaScript

$(".colab-select option").each(function (idx, val) {
       $(this).siblings("[value='" + $(this).val() + "']").remove();
  });