ul
{
    list-style-type: none;
    width: 20%;
    margin: 0;
    padding: 0;
}
li a
{
    display: block;
    background-color: lightgreen;
    color: green;
    padding: 12px;
    text-decoration: none;
    font-family: Arial, Helvetica, sans-serif;
}
.activo
{
    background-color: greenyellow;
    color: rgb(106, 107, 106);
    font-weight: bold;
}
li a:hover:not(.activo)
{
    background-color: greenyellow;
    color: darkgreen;
    font-weight: bold;
}