The Jet2holidays livery (which is what the entire A321 fleet currently wears) came to be after Jet2 leased a few 757s from Allegiant one summer. Jet2 then started using a revised scheme and that’s basically lead to where we are now, with a mix of the red and silver .com liveried planes and Jet2holidays liveried ones.
But maybe it’s a good idea to go back to the livery in question here, the Airbus one. We do have a separate Jet2 thread which got created the other day in general discussion for more discussions about it 