I emailed MS Motorcycles (John Chrichlow) who took care of the paint side of Hughie Hancox's expert Triumph restorations to ask if he could oblige with Ariel Maroon. I was expecting no more than the usual "Yes" or, more probably, "No" answer but instead he replied immediately & at length on the subject leaving me both amazed & impressed. His email is worth reading so I'll take the liberty of quoting it in full:-
"The first thing we have to understand is, although motorcycle manufacturers of the day were 'Apparently' offering a particular models in a particular colour, in practice, not all the bikes left the factory in exactly the same shade. Most motorcycle factories (I know Triumph did) used (At least) two different paint suppliers, who would have supplied 'Their' variant of a particular colour, there would also be shade variations of the same colour in batch to batch from the same supplier. In practice there would have been many original shade variations of a particular colour although mostly very similar.
I have original 'New Old Stock' Triumph mudguards finished in Silver Sheen that (Even an untrained eye) can see that they are 'Different'. The other problem we have is that if someone brought me a 50 year old tank to try to match the colour, I could only use the sample I had in front of me (Which would probably be faded or dirtied over the years) so although my colour may be very close to the sample (Trying to allow for fading) it may not look exactly the same as the colour when it was freshly painted. This is why we now see so many 'Variations' of an original colour, even though the paint was matched to an original finish.
Anyway! back to your bike. I am not that well up on Ariels, more of a Triumph man. However! I do have three formulations for Ariel 'Maroons' written down in my formulation book that I must have matched many years ago. One I have listed as Ariel Maroon 1962-1966,
The second is listed a Ariel Claret (I think I did an old Square Four for Jim Lee (Ariel marque specialist) in this colour.
The third is a colour I picked up from an Ariel Owners Club site stating that BLMC Blackberry (BLMC 3) was a good match for Ariel Maroon (These 'May' be variations of the same colour).
The problem I now face is that my paint mixing system is an old Cellulose system and over the years certain pigment tinters have been discontinued preventing me from mixing to an old formula. I have checked my old formulations and can only presently mix the Ariel Maroon 1962-1966 (The other two contain discontinued tinters on my paint mixing scheme).
This colour 'may' be the same as the older colour but I am not sure; you may have to do a little research. I would have matched the colour sample I had in front of me, so, although it may have been a variant of the same original colour, my paint would have been formulated to match that particular sample. It may pay you to contact Jim Lee, I think he does some work with the V.M.C.C. relating to Ariels.
I didn't realise that I could no longer mix two of the paints until I checked my formulation book, it must have been many years since I last mixed them. Paint may be available in a different medium e.g 2-Pack of Basecoat from another supplier. Take a look at BLMC Blackberry (BLMC 3) and Ford Black Cherry (Both of which I can no longer mix in cellulose on my paint mixing scheme).
If you have any problems, come back to me and I will see if I can come up with anything. All the best for now.
John Chrichlow. (M.S.)"
After reading this, it seems to me that the most important thing is to pick a modern equivalent of Ariel "Maroon" whether that be BMC Blackberry, RAL3007, etc. which is repeatable, and to make a note of the colour code somewhere (perhaps on the bike?). Then if, for example, the petrol tank has to be re-painted after damage at some future point in time, you will know the code that will ensure the re-painted tank continues to match the colour on the rest of the bike.
By the way, in addition to Ford "Black Cherry" mentioned by John Chrichlow I have also come across in the forum archives another Ariel Maroon equivalent quoted by someone, viz: Mercedes Benz (1968 and later) "Dark Bordeaux" DB 573 (PPG brand paint, DDL 50666D).
What still leaves me confused is the mention in John Chrichlow's email of 2 Ariel Maroons, viz: Dark Claret & 1962 - 66 Maroon as I have never seen an Ariel Two-Stroke in Marooon.
Incidently, a line up at an Annual Rally of Ariels finished & identified in all these different modern Maroon equivelents as well as a couple of "original & unrestored" examples of Maroon Ariels, would be very interesting.