Yes, currently the Colosseum staff is requiring visitors to purchase tickets in advance and arrive with their ticket downloaded to their smartphone or tablet.
How can I skip the ticket lines?
Advanced reservations are required if you would like to skip the ticket line at the Colosseum. The purchase of a guided tour will allow you to enter with a tour group and skip the ticket line. Please note that there is a mandatory security check for everyone entering the Colosseum and that this security line is different from the ticket line.