U's striker Freddie Sears slammed home his fourth goal in five matches in the 55th minute to seal the points.
Colchester goalkeeper Sam Walker brilliantly denied Andy Proctor's header early on, while U's striker Freddie Sears was foiled by Preston keeper Thorsten Stuckmann., which rattled the post.
But Joe Garner's header from John Welsh's cross looped over the bar for Preston late in the half, as both teams attempted to break the deadlock.
Sears' low shot flashed wide, but the former West Ham youngster made no mistake 10 minutes after half-time when he converted from close range after Jabo Ibehre had latched on to George Porter's pass and lifted a shot towards goal.
Preston's Lee Holmes hit the crossbar with a curling shot with 18 minutes to go.
But the visitors' hopes were ended when defender Wright was sent off following an off-the-ball altercation with Ibehre with eight minutes remaining as Colchester secured a crucial win.
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- Freddie Sears