JSFiddle - React, Tailwind, and code Playground

HTML

<div class="flexnav">
    <ul>
        <li><a href="#">Ссылка</a></li>
        <li><a href="#">Ссылка</a></li>
        <li><a href="#">Ссылка</a></li>
        <li><a href="#">Ссылка</a></li>
        <li><a href="#">Ссылка</a></li>
    </ul>
</div>

CSS

.flexnav li a {
    color: #fff;
    -webkit-transition: color .2s ease-out;
    -moz-transition: color .2s ease-out;
    -ms-transition: color .2s ease-out;
    -o-transition: color .2s ease-out;
    transition: color .2s ease-out;
}
.flexnav>li>a {
    display: block;
    padding: 18px 22px;
    font-weight: 300;
    font-size: 18px;
    text-decoration: none;
    text-transform: uppercase;
}
.flexnav li a:hover {
    color: #fff;
}
.flexnav ul {
    position: absolute;
    list-style: none;
    left: 0;
    margin: 0;
    padding: 0;
}
.flexnav ul ul {
    left: 244px;
    top: -1px;
}
.flexnav ul li {
    display: block;
    position: relative;
    padding: 0;
    margin: 0;
    border-top: 1px solid #fff;
}
.flexnav ul li a {
    background: #47718B;
    padding: 12px 22px;
    display: block;
    width: 200px;
    text-decoration: none;
}
.flexnav ul li a:hover {
    background: #4D6C80;
}