Как сделать, чтобы кнопка поменяла цвет при наведении? Bootstrap

Html

<div class="container-fluid banner">
                <div class="row">
                    <div class="col-md-12">
                        <nav class="navbar navbar-md">
                            <div class="navbar-brand">
                                Логотип
                            </div>
                            <ul class="nav">
                                <li class="nav-item">
                                    <a class="nav-link" href="#">Создать карточку</a>
                                </li>
                                <li class="nav-item">
                                    <a class="nav-link" href="#">О нас</a>
                                </li>
                                <li class="nav-item">
                                    <a class="nav-link" href="{% url 'about'%}">О нас</a>
                                </li>
                            </ul>
                        </nav>
                    </div>
            </div>

Css

body{
    margin:0;
    padding:0;
    background:#fff;
    font-family: 'Raleway',sans-serif;
    color: #fff;
}
.banner{
    height: 100vh;
    width: 100%; 
    background:url('https://sun9-60.userapi.com/impg/zdEQZSSQ5Q7kJ3TwpspalbtIgvq6ZH8hHdp8CQ/839gOvLA-cw.jpg?size=2560x1707&quality=95&sign=2515e33ff7d4fcb11f3e9655be269350&type=album');
    background-size:100% 100%;
    background-position: cover;
    image-rendering:-moz-crisp-edges;          /* Firefox        */
    image-rendering:-o-crisp-edges;            /* Opera          */
    image-rendering:-webkit-optimize-contrast; /* Safari         */
    image-rendering:optimize-contrast;         /* CSS3 Proposed  */
    -ms-interpolation-mode:nearest-neighbor;   /* IE8+           */
}
.banner .navbar{
    margin-top:1%;
}
.banner .navbar-brand{
    color: #fff;
    font-size:1.8em;
    font-weight: 700;
    margin-left: 10%;
}
.banner .nav{
    margin-right:5%; 
}
.banner .nav li a{
    color:#aaa;
    font-size: 1.1em;
}