JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://designmodo.github.io/Flat-UI/dist/css/flat-ui.min.css">
<link rel="stylesheet" href="http://designmodo.github.io/Flat-UI/dist/css/vendor/bootstrap.min.css">
<script src="http://designmodo.github.io/Flat-UI/dist/js/flat-ui.min.js"></script>
<script src="http://designmodo.github.io/Flat-UI/docs/assets/js/application.js"></script>
<select class="form-control select select-exemploa" data-toggle="select">
    <option value="0">Choose hero</option>
    <option value="1">Spider Man</option>
    <option value="2">Wolverine</option>
    <option value="3">Captain America</option>
    <option value="4" selected>X-Men</option>
    <option value="5">Crocodile</option>
</select>

CSS

/* Muda a cor verde para preto */
.select2-drop .select2-highlighted>.select2-result-label {
    color: #fff;
    background: #000 !important;
}
/* Necessário por causa do !important adicionado anteriormente */
.select2-result-selectable .select2-result-label:hover, .select2-drop .select2-result-selectable .select2-result-label:active {
    background-color: #e1e4e7 !important;
}


.select-exemploa .select2-choice {
    color: #fff;
    background-color: #E87E04;
}
.select-exemploa .select2-choice:hover,
.select-exemploa .select2-choice.hover,
.select-exemploa .select2-choice:focus,
.select-exemploa .select2-choice:active {
    color: #fff;
    background-color: #F4B350;
    border-color: #d35400;
}
.select-exemploa .select2-choice:active {
    background: #F9690E;
    border-color: #d35400;
}
.select2-container-disabled.select-exemploa .select2-choice,
.select2-container-disabled.select-exemploa .select2-choice:hover,
.select2-container-disabled.select-exemploa .select2-choice:focus,
.select2-container-disabled.select-exemploa .select2-choice:active {
    background-color: #F9690E;
    border-color: #d35400;
}
.select-exemploa .select2-choice .select2-arrow {
    border-top-color: #fff;
}

.select-exemploa {
    margin-top: 32px;
}