Chesterfield have now won six of their 12 league games this season and all of them have come via Saturday afternoon kick-offs.
By contrast, the majority of their six defeats have come in midweek.
Two individual errors gifted Chesterfield this latest victory. Home keeper Aidan Davison was at fault for the opening goal which arrived in the 25th minute.
Davison dropped a cross from Paul Hall and although he managed to save Colin Larkin's first shot it was Larkin himself who buried the rebound.
Colchester could not get going in the first half and the closest they came to a goal was a header from George Elokobi which visiting keeper Barry Roche easily caught under his bar.
It got worse for Colchester because Elokobi then made a mistake which enabled Hall to add a second goal in the 49th minute.
Teenage left-back Elokobi hesitated in the box and this enabled livewire winger Hall to disposes him and fire home a shot on the turn which gave Davison no chance.
Colchester, unbeaten in their previous five matches, threw caution to the wind by introducing attacking substitutes Richard Garcia and Neil Danns
Australian frontman Garcia almost pulled a goal back with a header and striker Gareth Williams was only inches away with a header himself.
The Essex club finally pulled a goal back in the second minute of injury time when Chris Iwelumo beat Roche with a 20-yard shot that flew in off the underside of the bar.
It was Iweumo's fourth goal of the season but it came too late for his side.