redoc/lib/common-components/Tabs/tabs.css

ul {
  display: block;
  margin: 0;
  padding: 10px 0px 0 0;
}

li {
  list-style: none;
  margin: 0;
  display: inline-block;
  padding: 5px 15px;
  background-color: #262673;
  border-left: 1px solid #1C1C50;
  border-bottom: 2px solid transparent;
  cursor: pointer;
}

li.active {
  border-bottom: 2px solid blue;
}