Visitors Colchester took the initiative early on when, after five minutes, Mark Goodlad risked injury by saving bravely at the feet of the oncoming Neil Danns.
A scrappy half produced little entertainment apart from the occasional set piece.
Kevin Watson's 14th minute corner was met by an eager Wayne Brown, who beat Sam Collins to the ball but headed over Goodlad's bar.
Vale's only chance of the opening 45 minutes fell to Michael Walsh when he attacked a Craig James free-kick but watched his header bounce wide of Aidan Davison's right post.
The U's had Liam Chilvers dismissed on the stroke of half-time after he was shown a second yellow card.
The Valiants came out brighter after the re-start but still struggled to use the extra man to their advantage.
James almost put his side into the lead after 51 minutes when his 25-yard left-footed free-kick dipped barely over.
Numbers were evened when Michael Cummins became the second player to pick up two yellow cards after 68 minutes.
The referee became the centre of attention yet again 14 minutes later when he controversially sent Vale substitute Levi Reid walking for a soft tackle on John White.
Vale tried to push forward but with a depleted team couldn't create any chances. Steve Rowland's 90th minute comfortable long-range low drive proved their best attempt.