Teammates for the Welsh National team merely a few days ago, the two flag-bearers of the Red Dragons' promising youthful influx will now be locking horns on Sunday afternoon.
And while Nottingham Forest starlet Johnson's footballing tuition is perhaps more well-versed than Colwill's - who only made his professional bow in February - you would still feel that the Cardiff City young gun will be chomping at the bit to engage in battle with a player he knows very well.
After shooting to prominence in astronomical fashion following Mick McCarthy's arrival at the club, he is now beginning to really impose himself in the first team picture, leading many supporters to believe he is deserving of a regular starting place.
A positive substitute cameo against Severnside rivals Bristol City before the International break was enough to incite optimism, and though their conquest for victory culminated in defeat, Colwill's endeavour, trickery and desire to create in the closing stages enthralled the Bluebirds faithful.
It is a dimension of play that, barring one or two exceptions, they are yet to truly see an individual adopt in City colours this term. Far too often, static movements and a distinct lack of an attacking fluidity has been on show, however, the academy graduate evidently carries the quality to breathe some extra life into this side.
Whether he is licensed the opportunity is yet to be seen- Leandro Bacuna and fellow International Mark Harris will both provide budding competition, though the deadline day departure of divisive winger Josh Murphy has freed up space in the attack.
Meanwhile, Johnson has made an impressive initiation to life in the Championship after dazzling on loan at Lincoln City last season, proving just why he had earned Premier League interest over the summer.
In the five games in which he has featured in thus far, he bagged a key late equaliser against Derby County in the East Midlands Derby along with assisting in Forest's opening fixture at Coventry City.
Clearly the most potent threat in Hughton's ranks at the minute, Johnson's presence is illuminated from his peers with a further seven created chances, a statistic which ranks him highest in the squad by a fair way.
He will also be looking to utilise his speed, fleet-footedness and deft body shifts to disassemble the Cardiff backline, who enforce solidity and a physical prowess but often tend to come undone against pacy opponents.
McCarthy, along with Johnson's Welsh compatriots Kieffer Moore, Colwill and Harris will all be conjuring ideas on how to nullify the 20-year-old, however, doing so will be even trickier given his positional flexibility.
To date, he has spent time working his magic out wide as well as more centrally as an attacking midfielder, while even undergoing spells playing off the shoulder, too.
As two highly-rated young prospects reverse loyalties and go neck and neck for victory, it will surely be interesting to see how this contest pans out.
The clash between creative midfielders Colwill and Johnson promotes a plethora of similarities, however, the soon-to-be-commenced battle that Joel Bagan and Philip Zinckernagel may well carry out promotes stark contrasts.
Instead, is it a contest of youth and experience; Cardiff defender Bagan has only played 18 games of senior football, whereas Zinckernagel boasts over 250 appearances in the professional game.
Despite Bagan's relative lack of experience, though, he has showed few flaws upon being handed the first choice left back role after club stalwart Joe Bennett left over the summer and is quickly growing into that berth.
It is clear that he is much more comfortable defensively as opposed to going forward, yet, an increasing eagerness to get higher upfield and help out attacking plays has been showcased in recent weeks.
Zinckernagel is also adapting to fresh roles and responsibilities following his summer switch from Watford on a season-long loan.
He will now be one of the main forces at Forest this term, and having showed glimpses of quality during his half-season stay in Hertfordshire, big things will be expected.
Signed by Watford from Norweigan outfit Bodo/Glimt last December, the versatile attacker amassed an outstanding return of 19 goals and 24 assists in just 29 Eliteserien fixtures which promptly led to the Hornets stinging for his signature.
So far, his Forest stint has started brightly with a goal and an assist, but he is still getting to grips at this stage and may well be the toughest opponent that young Bagan has faced so far this campaign.
An inventive outlet on the right flank as well as an efficient ball-carrier into deep areas, it will come as a real test for the former Notts County loanee - yet, if he can overcome Zinckernagel, it really would speak volumes of his development over the last 12 months.
Ryan Giles V Fin Back
This may be a duel that Bluebirds wide man Ryan Giles will be licking his lips towards after roaring out of the blocks at the Cardiff City Stadium.
It looks likely that Hughton will elect young full-back Fin Back for the affair following Jordan Gabriel's departure to Blackpool and the absence of Arsenal loanee Jordi Osei-Tutu- who spent an injury-stricken campaign at Cardiff last time out.
When fit, the Hale End academy product would undoubtedly provide a stern test for the impressive Giles, however, Back has only made four competitive appearances for the Reds' first team and will have the unenviable task of neutralising one of the Championship's most exciting performers so far.
Although it was widely believed that he would fill the vacated left-wing-back role upon his arrival on loan from Wolverhampton Wanderers, McCarthy instantly identified his attacking qualities and decided to use the 21-year-old further forward, a decision which has quickly paid off handsomely.
Possessing electrifying speed, a real engine and a precise crossing ability which allows Cardiff to optimise the aerial threat within their squad, he has already contributed four assists and is showing few signs of letting up - in fact, at his age, he will only improve, a scary prospect for second-tier defences.
An intelligent operator, Giles can also make darting runs in behind defences, meaning Back can not afford to take his eye off the blitzing left-winger at any occasion across the encounter.
Quite how the youngster will fare against his opponent remains a mystery, although given his early-season performances, many will unsurprisingly expect Giles to continue in the same vein and light up the City frontline.