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Speaking from a position of relative ignorance I'd be weary of changing just one caliper on a car with a potentially different one.
If they are exactly the same caliper and it's only a colour difference then the only problem I can see is if the other rear isn't working at its fullest.
(assuming the pads are similar wear). So I'd check and service that one at the same time. -
Caliper is probably only part of the issue. The slider pins do wear over time (the male prong bit as well as the female bit within the caliper body) and get more slack in them/sticky. Worth changing the lot at the back if your brakes have needed that much 'fiddling' for so many years.
The bracket part is sometimes at fault too, where the edge of the pads rests on the bracket they eventually wear grooves into it, then when you put new pads in, they just don't move. You can grind this part down with an angle grinder to get it all level/smooth again, but you can only do this once, take off too much material and the pads will eject when you brake lol
One of the rear calipers on my Mk1 Octavia VRS is seized. If I buy this to replace it with, how fiery and explosive will my death be?
https://www.ebay.co.uk/itm/Brand-New-Skoda-Octavia-1-Rear-Brake-Caliper-Left-Nearside-OE-No-1J0615423E/253115344096?
Only problem is that it's not green, but I reckon I can put up with that compared to £80 for a painted OEM ebay one or £200 for the proper Skoda UK one, as long as it's not a terrible idea?