Steven Gillespie gave the U's the lead but Sam Baldock finished neatly from close range to equalise and netted again from Daniel Powell's incisive pass.
Baldock completed his treble with four minutes remaining after Luke Chadwick's shot was parried to leave Robinson delighted.
He said: "I asked them to go out and enjoy it in the second half and go and play football. There were so many things that went wrong that I could keep you hear all day telling you.
"But when we came in at half-time 1-0 down, I said to my players that we should go out and show everyone how good we are and go and believe they are good players and they did that.
"Colchester had more chances in the second half than the first half and I don't think we were that bad before half-time. We didn't play our football in the first half but we limited them to one chance and they scored from it."