I'm not sure how to edit the selection box created by <select class="form-control">, here's what I have:

  <select class="form-control">
    <option>00:00</option>
    <option>01:00</option>
  </select>

and my css:

.form-control {
  width: 60px;
  height: auto;
  display: inline;
  border: none;
  border-radius: 0;
  border-bottom: 1px solid black;
  padding: 0;
  box-shadow: none;
}

this gives me:

but now how do I modify the actual box created by this select element? I want to get rid of that ugly yellow color, smooth the borders ... etc.. etc..

fiddle of the code above: https://jsfiddle.net/08zrLjgc/