Nine points off the top in fifth, Warrington needed a winger to bolster their squad.
At just 19 years of age, Bell already has three appearances for The Cumbrians, one of which in the league.
Carlisle will hope his departure won’t damage their relegation battle, as they sit in 19th.
Coulton, also 19, signed his first professional contract for the Lilywhites last summer.
The under-19s Scottish International featured on the bench three times for Preston last season.
With a tough game coming up on Saturday against third-place South Shields, the duo will hope to make immediate impacts.
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