Scott US 267 Or 279Bf, Changeling?

Imodius,
My apologies for being a bit blunt, but you completely missed the lesson contained in Don's post above with the 4 scans of Scott 278 from the Siegel website. The scans are made by different people, at different times, on different equipment, with different settings and adjustments. Doing ANY color analysis on such a motley collection of scans has absolutely zero validity. ZERO! Sorry, but the same can be said for your assemblage of 279B images from their site also.

I'm a novice to say the least in these stamps, I have a few of these and as far as I have taken them is to distinguish the three types (yep..that's it)
I thought why not give your chart a try you could be on to something!
Threw my screen, I couldn't get a single colour remotely close to any examples given by anyone.
Software doesn't seem to support true colours or it's the screens (maybe a individual set-up could achieve this?) but threw the transfer or compression of the file, pigment or what have you appears to be affected ...least in my attempt
Not saying it's not working on your end.

12 perfs top 11 bottom something strange there

Red rose
perforations are measured by the size of the perforation not the actual number of indentations themselves
I'm gathering that's what you mean from the way you wrote "perfs"
Some Great Britain you can count,
But with these you need a specific gauge

Looks odd when the perforations aren't aligned side to side or top and bottom, stamps are dry when they perforate them. perforaters do multiple rows at once

I think it's the difference between line and comb perforations. But I could be corrected