There's a lot of conflicting advice - the problem is that it is all true !!
Your car was probably originally filled with "green" coolant, but if the proper service schedule was followed, this would have been replaced, after a proper flushing, by "yellow" coolant but, if not done by a Jaguar Dealership, may have been replaced with more "green" or maybe, it has never been replaced at all.

What I did ('97 car) was to drain the system completely, and then do two complete fill / drive / flush routines with ordinary water of about an hour each. By the second one, the "drain liquid" was pretty much clear - i.e. water.
After that, it's safe to refill with a modern "orange" or "red" coolant which meets the Ford / Jaguar specification. I did lots of research, and the main issue, as noted in many posts already, is that you don't want to mix different types as they can react with each other and turn into a sort-of jelly which is not good news.
I did mine two years ago, and no problems. Although it's supposed to be OK for five years, I'll probably renew it this coming summer - cost is fairly negligible in the great scheme of things !!

 

Just to be different, I use purple.

Pentosin 8114107 Coolant/Antifreeze SF 1.5 Liter (Purple)

 

OK, so it's been a month and I bought the Xerex yellow. Now it's too cold to flush the system so I'll wait a bit for warmer weather. I think I overthought the whole process.

 

I guess the BIG question is Zerex Dex-Cool Antifreeze a good choice? Is it to Jaguar specs? The dealership charges almost $50 for antifreeze while the Zerex is $15.

 

Check the required coolant specs in your car's owners manual. Then look for those specs printed on the label of the jug of whatever coolant you are considering. If the specs are clearly there, then you're good to go....

 

Once more (with feeling) the ONLY thing that matters is the specification. Not the colour, not the name, not the supplier, not the retailer.

 

UNLESS, a previous owner flushed out the system and used a different fluid. Is not that the correct? If the service history is not known, then a flush is always recommended, right? Mine is a colour I've never quite seen before!