That's a nice spreadsheet!
When it comes to purple podded varieties i have my suspicions about why some lines wash out or are more variable than others. You need the dominant gene "A" in combination with at least one copy of each co-dominant genes "Pur" and "Pu". But i suspect that you get better pods if you get homozygous alleles for both of the co-dominant genes. My red-podded line is pretty stable for purple genes as it stand right now, pretty much no variation other than spitting out yellows occasionally. I don't think you need the "A" gene in homozygous form, but if you don't want yellows or green pods spitting back out, then you yes you do.
Anthocyanins are also temperature and environmentally affected, so it may not work as well in certain climates. Perhaps anthocyanin plants get purple well in my area because i am both at high altitude with a thinner atmosphere (so more intense sunlight), but also we have a semi-arid climate, so few clouds. But not as hot as say Texas.
All these factors combine may explain why it is so hard getting good tasting purple podded varieties, let alone red podded ones.
p.s. do you happen to have those "o<y" golden yellowish pods in your collection or just reading about them? I've noticed some people seem to have some yellow podded breeding lines that seem a darker yellow that does not fade as much, and i'm curious to know what is going on.
I will be growing out another generation of [orange-pod x gp] in hopes of a deeper yellow combination, but as of now i have not seen anything interesting. "gp" fades as the season goes, while orange-pod increases as the season goes. Theoretically it could be a nice combination.
p.s.s. 
i'm not sure where you would put it in your spreadsheet, but when the "b" modifier gene is combined with a purple pod you get a sort of maroon red, and i suspect if combined in a red pod with gp underneath you would get a "peachy pod" which would look really cool like rebsie's original "peachy pod".
https://daughterofthesoil.blogspot.com/2008/07/red-podded-pea-update.html
I don’t have “o<y”. (Yet. 😁)
If JIC has a line with it specifically I haven’t found it, but that is likely my lack of search skills.
Next time I request accessions I’m going to ask for some “o” and “gp” so that I can compare.
Orange pod...doesn’t the pigment show up in the fibre of the pod?
If the pod has fibre, it won’t be a great snap/snow type. Right?
I didn’t include the chart with the reds.
Still trying to get the various gene combinations involved straight in my head.
Interesting observation on “peachy” pods...
