how to change css of select tag code example

Example: change option tag css

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet" />
<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap-select.min.css" rel="stylesheet" />
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap-select.min.js"></script>

<select class="selectpicker">
  <option>Mustard</option>
  <option class="special">Ketchup</option>
  <option style="background: #5cb85c; color: #fff;">Relish</option>
</select>