<select class="mdb-select colorful-select dropdown-primary" multiple searchable="Search here..">
<option value="" disabled selected>Choose your country</option>
<option value="1">USA</option>
<option value="2">Germany</option>
<option value="3">France</option>
<option value="3">Poland</option>
<option value="3">Japan</option>
</select>
<label>Label example</label>

<select class="mdb-select" multiple searchable="Search here..">
<optgroup label="team 1" >
<option value="1">Option 1</option>
<option value="2">Option 2</option>
</optgroup>
<optgroup label="team 2">
<option value="3">Option 3</option>
<option value="4">Option 4</option>
</optgroup>
</select>

// Material Select Initialization
$(document).ready(function() {
$('.mdb-select').material_select();
});