<ul>
  <li><span class="link">未訪問リンク</span></li>
  <li><span class="visited">訪問済みリンク</span></li>
</ul>

ul {
  list-style-type: none;
  cursor: pointer;
  position: relative;
}

li {
  position: relative;
}

span:before {
    content: "";
    position: absolute;
    top: 0.55em;
    left: -0.7em;
    width: 4px;
    height: 4px;
    background: #00a1db;
    border-radius: 9999px;
}

.link {
}

.visited:before {
  background: silver;
}