SDSD
Stop believing in colour! As Grant said it is just the arbitrary use of dye. Just ensure that the stuff going in is glycol - there are several actual compounds, but they all have glycol in the ingredient name somewhere. The Tasmanian club are misleading you as are loads of the other stuff you are quoting.
FWIW at X,000 miles distance, I do not believe for an instant that you have a head gasket failure, I suspect Jagboi is right about coolant residue. Flush, refill with glycol antifreeze, run it for several journeys. If anything appears again, then do a test for gasses in the coolant:

Your garage will have this sort of tester.

 

I hope it's very likely to be residue or muck or something like that, but I don't want to think that just because it's the better option. I generally prepare myself for the worst. That way, at worst it's what I expected, and at best, it's a pleasant surprise.

I'll have to check an actual bag when I next go to an Autobacs to see what exactly is in there, assuming they even list it on the back, but all I'm saying about colour is what I read about green signifying glycol (IAT). That, you say, is no longer be the case. So I shall compare the ingredients lists when I next pick up a bag.

Lady Mary is at 75,000 km and change. She has been well pampered under my ownership at least, and I have taken her on extended road trips on multiple occasions. So I agree that she shouldn't be suffering from a head gasket failure--and if she is, it doesn't affect her on-road performance in the least.

Anyway, I should know more in a few days....
(And I'm still waiting on parts from Australia.)

 

Head gaskets on the V12 are generally needed after a SERIOUS overheat event.

The mixing of coolants is more common than warm beer in the UK, so dont blame yourself too much.

Just get the mechanic to fill your container with what he is putting in YOUR car, simple.

Down here, workshops change suppliers constantly, usually price, etc driven. "All the same etc etc" is the sales pitch, then this happens, and the run for cover is quicker than politicians caught with their fingers in the Govt cookie jar.

When you match my PreHE at 655000kms, and ALL as made in the UK, then the worry can start. This beast leaks oil, uses coolant, so I top it up and keep on thundering down the road, life's too short to worry.

 

Looking up old receipts, I see the shop usually uses Bosch LLC.

This has been a very educational thread. Before it started, I just knew (or thought I knew) "shove in more of the same colour, pre-mix" and had no idea what the differences, if any, might be. Another post (in Japanese) on coolants I just checked also said "don't worry about mixing colours", but it was mum on the topic of IAT and OAT and all that.

Off topic, I found British warm beers to be surprisingly palatable when I visited. The not-being-served-two-degrees-above-freezing means that the flavour can make itself known. Which were generally decent, though I much preferred the ales from northern England to the south.

 

OK, I had another CRAFT moment.

Get your guy to pay very close attention to the small hose travelling aft of the coolant header tank. This goes thru the grommet near the bonnet lock, and down to the atmospheric tank in the LH wing aperture.

This hose AND the tank will be badly contaminated with this GOOP.

This MUST be cleaned out, the tank then filled to 1/2 with new coolant, and returned to its hiding hole.

Access to that tank is, wheel off, closing panel removed, and there it is. BIG Black plastic tank, about 6ltr++ capacity.

 

Good point. The atmospheric collection tank was checked a couple of years ago, but with this muck in the system, it could definitely use another look-see. I know there's a Japanese site which shows the removal of that tank I can use to show the mechanic. I think I might take a cycle down to the garage tomorrow.... (So long as the weather forecast pans out and it's not actually raining.)