Steven Alzate netted the opener on his first senior start, before Koroma took centre stage with two strikes before the break, and then sealed the hat-trick with a second half penalty.
Orient made five changes to the side which lost out 4-1 at Stevenage in midweek with goalkeeper Charlie Grainger making his first start of the season, while Freddy Moncur and Steven Alzate made their first league starts for the club. Tom Parkes also returned from injury, while Sam Dalby returned to the starting line-up.
They made way for Sam Sargeant, Michael Clark (ankle), Sammy Moore, Gavin Massey (suspended) and Paul McCallum (knee).
It was the hosts who started the brighter and Grainger was the busier of the two keepers in the early stages. Nicky Hunt put his body on the line to block a Marlon Jackson effort before the O’s keeper tipped over a Ryan Bird header.
Bt with the first foray forward for the O’s they took the lead. Semedo won the ball in his own half, played the ball to Moncur who in turn fed Koroma.
The winger produced a mazy run down the left before playing the ball into the box and Alzate was there to slot home off the inside of the back post.
One soon became two for the O’s though as Koroma pounced on a through ball from Dalby 13 minutes in and he was through on goal with only Day to beat. The attacker kept his nerve and slotted low past the keeper to double Orient’s advantage.
That had certainly quietened down the home faithful, and chances became few and far between with the game being played in midfield.
The only chance following the O’s second fell the way of the Exiles Dan Butler, but he fired his effort well off target.
Grainger was back in action on 35 minutes and he did superbly well to tip over Jackson’s curling goalbound effort, before Kennedy deflected Alex Samuel’s fierce effort as the Exiles forced two corners in quick succession.
As the half drew to a close the hosts had one final chance as Butler curled a free-kick narrowly wide of the target with Grainger at full stretch.
There was still time for the O’s to add to their tally and it was another quick breakaway.
Semedo played the ball through to Dalby who run through on goal. He could have been selfish and taken the shot himself but he laid it into the path of Koroma who was left with the simplest of finishes to send Orient in 3-0 up at the break.
Newport made two changes at the break, with Sid Nelson and Darren Jones replaced by Joss Labadie and Sean Rigg, while the O’s remained unchanged.
Orient had the first opportunity of the second period and it was that man Koroma again on the counter attack. The attacker was able to round Day in the Exiles goal before falling to the ground, and referee Gavin Ward deemed that Koroma had made a meal of the trip and cautioned the youngster.
Up the other end, Hunt headed a ball in behind as the hosts looked for a way back into the game, but the O’s were dealing with everything that came their way.
And the O’s had surely put the game to bed in the 63rd minute when Alzate’s trickery saw him felled in the box and referee Ward pointed to the spot.
There was a bit of a debate as to who would take the penalty, but it was to be Koroma and although Day got a hand to the effort it was too powerful to keep out and he celebrated his hat-trick – his first three senior goals for the O’s and become the first player to net a hat-trick for the club since Shaun Batt in the Johnstone’s Paint Trophy back on September 3, 2013.
Koroma was then given a rapturous round of applause shortly after as he was replaced by Tristan Abrahams who made his senior debut for the O’s.
Despite the comfortable lead, the O’s still looked to keep a clean sheet and Grainger did well to deny to parry Samuel’s shot before gathering the ball at the second attempt, and then Williams’ fizzed an effort across goal.
The impressive Dalby and Moncur were then brought off in the closing stages with Victor Adeboyejo and Teddy Mezague coming on in their place as time began to tick away.
Abrahams wanted to get in on the goalscoring act as well, but his effort from distance was held by Day, and that proved to be the last action of the game as the O’s picked up a much-needed victory.
NEWPORT COUNTY AFC: Day, Butler, Nelson (Rigg HT), Bennett, Jones (Labadie HT), Jackson (Williams 64), Samuel, O’Brien, Demetriou, Rose, Bird
SUBS: Bittner, Reid, Bignot, Owen-Evans.
BOOKED: O’Brien (30), Labadie (60)
ORIENT: Grainger, Judd, Hunt, Parkes, Kennedy, Moncur (Mezague 87), Collins, Alzate, Koroma (Abrahams 68), Semedo, Dalby (Adeboyejo 84).
SUBS: Sargeant, Moore, Ochieng, Happe.
GOALS: Alzate (8), Koroma (13, 45+2, 64 pen)
BOOKED: Koroma (49)
REFEREE: Gavin Ward.
ATTENDANCE: 3,378 (395 Orient fans)