The impressive U’s scored five times before the interval with strikers Kevin Lisbie and Clive Platt both netting twice to leave the Canaries completely shell-shocked.
It was all too much for a couple of supporters who ran on to the pitch after the visitors had made it 4-0 and threw their season tickets at manager Bryan Gunn before being ejected.
Paul Lambert’s side only managed to add two to their tally after the break, with Norwich pulling one back, but by then the match was over as a contest.
Debutant goalkeeper Michael Theoklitos had a nightmare start to his Norwich career missing his punch from an ill-advised Jon Otsemobor back pass to give Lisbie the opener after 10 minutes – and then failed to gather Lisbie’s low shot, allowing Platt to side foot into an unguarded net three minutes later.
Platt then coolly converted at the back post after Simon Hackney’s cross had been missed by everyone before David Fox’s curling free-kick made it 4-0 after just 22 minutes.
Many Norwich fans had started heading for the exits by the time Colchester made it 5-0 10 minutes before the break, Lisbie heading home with consummate ease after Platt had flicked the ball on.
Colchester wasted a couple of chances to stretch their lead early in the second half but Norwich at least made a game of it after that and pulled one back after 71 minutes when substitute Cody McDonald latched on to a flick from Grant Holt.
But Colchester swiftly re-established their five-goal advantage as another substitute, David Perkins, fired home a superb left-foot volley from just outside the area – and a tap-in from Scott Vernon in the final minute completed an opening day of abject misery for Norwich.