I believe the idea is that random audits check whether the barcode matches the human-readable part, and in the extremely unlikely even problems are found they simply hand-recount _all_ the ballots ignoring the barcode.
(Taking a bit more pointed tone than I usually would, because of the amount of misinformation around this general topic and because of annoyance at people putting less effort in than election workers, from secretaries of state down to volunteers, and casting shade from the laziness of their armchair. Thank you to all the people spending their time trying to secure elections!)
Did you try searching for "colorado voting audit"?
There's a page on their SOS site... https://coloradosos.gov/pubs/elections/auditCenter.html
Which even has a YouTube video on the process... https://m.youtube.com/watch?v=oKgSKh4utNo