French Stamp : #6 Or #6A ?

I suppose GeoffHa might have the correct information. I am not familiar with French stamps. I can find a listing of some 'shades.'

That listing mentions Scott 6 = Yvert 4: blue on white to bluish paper; Scott 6a = Yvert 4: darkblue on yellowish tinted paper; Scott 6b = Yvert 4b: blue on yellowish paper.

What often happens with 'shades' is that some has two distinct 'shades' and thinks they are the two listed shades, when catalogues, normally, list shade bands. It is very tempting to consider a palish blue and blue stamp as having to be the listed blue and dark blue, when they are both blue and dark blue is very much darker.

Purely from what I see posted on my own laptop, I am not convinced I am seeing any dark blue stamp. They look blue or pale blue to me. As remarked before, I do not know what the true colours are. I, only, can observe relative colours. I also do not know if Yvert and Scott talk the same language. At best I can observe someone on a website has linked two Scott listings to two Yvert listings. I do not know if that was correct.

From above listings, the dark blue colour must be on yellowish tinted paper. But is the source correct, or has someone copied information from Yvert and forced the Scott listings into those two choices.

On this site, I have seen people post Scott's purple GB stamps with a date of issue that correspond with SG lilac stamps, when SG lists purple as well, but from another period.

Here is an example from my own GB George V Simple Cypher collection. One of the cheapest shades is the blue-green one that, after two decades, has not popped up. I have a certified bright blue-green stamp that is unlisted. It falls in the blue-green shade band.



Would I have had the blue-green one, I might be tempted to shift the unlisted bright blue-green stamp in the cobalt-green box that is listed. Just because that is an empty box and looks a little like it but different from an ordinary blue-green or any of the other 'shades.'

Purely going by the SG specialised listing, I have the blue-green stamp. It, just, has an RPS certificate stating it is bright blue-green.

Great ! Thanks Bobby de la rue and NSK for all these informations !

Extracts from Yvert and Maury, and some copies from my collection. Apologies for the scan quality.