Q, a good one for Russ to chime in on, hopefully as the printing expert.
There are a lot of 3c 1861's and 1851-7's that are too faded to ID. A lot of the 1861's that are faded end up on eBay
with the seller trying to sell them as 64's! :( And the pinks have notoriously faded over the years, as the color isn't stable-- which is the reason why they started to add carmine and brown to the ink in the first place- the lack of stability.
As I recall, there is a stamped envelope from '61 that is pink, I don't collect them so I don't remember the Scott number U- something, which is the true pink that they were trying to use for the 3c stamp, but couldn't get the results they wanted.
Ashbrook described the "near pinks" and pigeon blood. And I know that there have been color and shade students for a long time- but I don't have any of the material. McClung is the person who categorized the shades by time period and rarity by looking at thousands of dated covers. Maybe Russ can chime in here with anything back in the archives.
Thanks again, Ray