We did indeed have 2 losses, but the A.P. Top 2 through 5 finishers (after C.U.) were Georgia Tech (11-0-1), Miami (10-2), Florida State (10-2), and Washington (10-2).
Had we beaten #1 Colorado in that game, there is zero doubt that we would have been voted ahead of all of the other 2-loss teams. It would have come down to Georgia Tech and us. For whatever reason, the A.P. voters that year just did not seem to have much respect for Georgia Tech. They had them second behind Colorado both before and after their Orange Bowl win over us, despite Colorado having a loss. Our theoretical win over Colorado would have given us victories over 4 Top Ten opponents and 7 Top-25 opponents. Georgia Tech beat a single Top Ten opponent and 4 Top-25 teams. And we would have just beaten the team they had ranked above Tech.
The A.P. voters really, really liked the 1990 Irish team all year long. There is a real chance that a win over Colorado would have given us the A.P. National Championship (the U.P.I. Coaches Poll would have gone to Georgia Tech).