(Missing) Pink Back And Other Hints To Identify The 2c Rose Carmine Color?

I just found this week the interesting "book" of the PSE called "Philatelic book of secret", part I and II. Especially in part II there are many colors explained, with the Pantone system. Of course this can only be a first indication, and for example the given Pantone colors of the 3c 1851/57 are quite funny sometimes, but for the 3c 1861 and the 2c 279B they are really helpful (if you have a Pantone guide).

But why I continue this old thread now is their explanation about the color of the 279Bc (rose carmine) about which my questions are above. I supposed that the 279Bc probably does not have a pink back which would be helpful in sorting all those 2c stamps. And PSE writes in this book that the UV light shows different reactions for the different 279B colors, and the rose carmine shows not orange but more carmine under UV light, and this, because it may have little or no aniline ink. If now the aniline ink is responsible for the pink back of the 2c stamps, the 279Bc should have no pink back.

If anyone wants to confirm this (maybe with looking at a real 279Bc or 267c) it would be interesting, also if I am wrong.

PSE also writes that they found a stamp very similar to the 279Bc but with different reaction under UV, so they call it "pinkish carmine" and it is not listed as such in Scott or sold anywhere like that. I don't know if you can search for a word in the PSE database on their website, but this would be interesting to see such a certificate.

(And last point, they didn't find any stamp which would fit the "orange brown" color, just as this was also mentioned above.)

I am going through a bunch of these right now, sorting 279Bc and 267c from a bunch of them that are mixed together and have sorted some looking to DIE examples. To further sort them but I flipped them over today and I have examples that are DIE 79 with no pink on the back but I have seen them in plate blocks with pink on the back in 267. I have also seen some examples that are DIE 83 and have no pink on the back as well as DIE 83 which have pink on the back, so a person still sort DIE 79 from DIE 83 even if the stamp has no pink on the back.