[Vlasenko Fedor]

<style>.min {
  color: red;
}

.max {
  color: green;
}
</style>
<table>
  <tr>
    <td>11</td>
    <td>22</td>
    <td>65</td>
    <td>14</td>
    <td>35</td>
  </tr>
  <tr>
    <td>39</td>
    <td>12</td>
    <td>84</td>
    <td>45</td>
    <td>38</td>
  </tr>
  <tr>
    <td>37</td>
    <td>39</td>
    <td>52</td>
    <td>38</td>
    <td>24</td>
  </tr>
</table>
<script>
HTMLCollection.prototype.forEach = NodeList.prototype.forEach = Array.prototype.forEach;
var min, max, val;
var allTd = document.querySelectorAll('td');
allTd.forEach(function(el) {
  val = +el.innerHTML;
  if (!min) {
    max = val;
    min = val;
  } else {
    if (val > max) max = val;
    if (val < min) min = val;
  }
});
allTd.forEach(function(el) {
  val = +el.innerHTML;
  if (val === min) el.className = 'min';
  if (val === max) el.className = 'max';
});
</script>

в 2 прохода