это в html:
<nav>
        <ul>
          <li id="about"><img src="assets/nav-about.svg" alt="Navigation bar about icon"><a href="./about">about us</a></li>
          <li id="services"><img src="assets/nav-services.svg" alt="Navigation bar services icon"><a href="./services">services</a></li>
          <li id="contact"><img src="assets/nav-contact.svg" alt="Navigation bar contact icon"><a href="./contact">contact</a></li>
        </ul>
</nav>

это в css:
nav li:hover {
  filter: brightness(1000000%);
}