select {
  letter-spacing:10px;
}

option {
  letter-spacing: 10px;
  color: red;
}

<select class="form-control" name="select" id="myselect">
   <option value="105">Option 1</option>
   <option value="106">Option 2</option>
   <option value="107">Option 3</option>
</select>