Full-time score from Hayes Lane
Defender Keaton was perfectly placed to head home his fourth goal in just eight games and send Justin Skinner's charges to a fourth win from their last six games.
The young Lions went into action on the back of a cracking 4-0 victory at QPR, and whilst not producing the same degree of free-flowing attacking football against Colchester, manager Justin was just as pleased at other aspects of his team's display.
"It was a good result from a tough game against a Colchester side who brought down a number of players with first team experience and on the fringes of the senior side," Justin told millwallfc.co.uk
"There are different ways of winning; last week we won at QPR with some good passing and movement. This week we had to dig in to come out of the game with a win.
"What pleased me the most was the mentality showed by our players of not wanting to lose. They blocked bravely, they produced last-ditch clearing headers, they really put their bodies on the line to earn this result."
Centre-half Keaton grabbed the game's only goal early in the first-half with a glancing header after Christian Mbulu had knocked the ball into his path as Colchester failed to clear their lines from a free-kick.
Whilst delighted at the defender's scoring prowess, boss Justin also singled out young strike duo Ebere Eze and Mikael Ndjoli for special praise.
"Keaton is a particularly good pro," he added. "He does everything right, is good at finishing, and his attitude is spot on.
"Today our two young forwards Ebere and Mikael really do deserve a mention. They played for the 21s at QPR last Tuesday, travelled up with the U18s to face Hull City on Saturday and then did some tremendous defensive work against Colchester.
"It has been a particularly gruelling schedule for them, but their effort has been phenomenal. They put in excellent shifts and deserve great credit."
Millwall: Girling, Parr, Chesmain, Wood, Nelson (Brown), Mbulu, Cowan-Hall, Romeo, Ndjoli, Eze, Twardek. Subs not used: Sandford, O'Donnell, Bray.