Navigation can't be edited directly and the .active menu item is swapped out with a ::before
pseudo element.
.rel a
is an overlay to make it working button, but needs matching hover effect.
For positioning the div.rel is collapsed
li {
margin: 4px;
width: 200px;
background-color: #bbb;
height: 30px;
list-style: none;
text-align: center;
}
li.active::before {
content: '4';
}
li.active a {
visibility: hidden;
}
ul li.active::before {
background-color: green;
}
div.rel a:hover~ul li.active::before {
background-color: yellow;
}
div.rel {
position: relative;
}
div.rel a {
position: absolute;
width: 200px;
height: 20px;
background: red;
color: #fff;
}
<!-- nav code can't be edited -->
<ul class="nav">
<li><a href="#">1</a></li>
<li><a href="#">2</a></li>
<li><a href="#">3</a></li>
<li class="active"><a href="#">4</a></li> <!-- <<<< This 4 needs to turn yellow when you hover the red button -->
</ul>
<!-- nav code can't be edited -->
<div class="rel">
<a class="overlay" href="#">Hover here turn 4 yellow</a>
</div>