HTML

html select required

<select name="color" id="color" required>
	<option value="" selected disabled hidden>Choose color...</option>
    <option value="R">Red</option>
    <option value="B">Blue</option>
</select>

select required

<label for="cars">Choose a car:</label>

<select name="cars" id="cars" required>
  <option value="">None</option>
  <option value="volvo">Volvo</option>
  <option value="saab">Saab</option>
  <option value="mercedes">Mercedes</option>
  <option value="audi">Audi</option>
</select>

required option for select tag

<!--- This option cannot be select and this will be default option too. -->

<option selected="true" disabled="disabled">Select a Option</option>

<!-- Here is a example : -->
<label for="payment">Choose a Type :</label>
<select name="payment" required>
  <option selected="true" disabled="disabled">Select a Option</option>
  <option value="recharge">Recharge</option>
  <option value="withdraw">Withdraw</option>
</select>