<ol>
  <li>item</li>
  <li>item</li>
  <li>item</li>
  <li>item</li>
</ol>
<br>
<hr>
<br>
<ol class="ol-type-2">
  <li>item</li>
  <li>item</li>
  <li>item</li>
  <li>item</li>
</ol>

ol {
  list-style: none;
  counter-reset: i;
}

ol li {
  counter-increment: i;
  font-size: 30px;
  padding: 5px 10px;
}

ol li:nth-child(even) {
  background-color: #ccc;
}

ol li:before {
  content: counter(i) ".";
  display: inline-block;
  background-color: #fff;
  color: red;
  width: 40px;
  height: 40px;
  font-weight: bold;
  border: 2px solid red;
  border-radius: 50%;
  text-align: center;
  line-height: 40px;
  margin-right: 20px;
}

.ol-type-2 li:before {
  content: counter(i, upper-roman);
}