Redaction Snippet

Obviously you wouldn't really use CSS to redact information, but the snippet serves as a clue to the reader that this information is hidden for a reason and they need to 'discover' it:

.redact {
  background-color: black;
  color: black;
}
<p>My name is Tristan and my number is <span class="redact">###-####</span>.</p>  

My name is Tristan and my number is ###-####.