Герман Зуяков

.nav__link{
     color: orange!important;
}

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" integrity="sha384-GJzZqFGwb1QTTN6wy59ffF1BuGJpLSa9DkKMp0DgiMDm4iYMj70gZWKYbI706tWS" crossorigin="anonymous">
  <link rel="stylesheet" href="./index.css">   <!-- Подключать позже Bootstrap!!!!!!!!!!!!!!!! -->

(function() {
    var link = document.querySelector("link[rel*='icon']") || document.createElement('link');
    link.type = 'image/x-icon';
    link.rel = 'shortcut icon';
    link.href = 'http://www.stackoverflow.com/favicon.ico';
    document.getElementsByTagName('head')[0].appendChild(link);
})();