It's fascinating that just 3 years after article date this [1] gets discovered, which is a fantastic pigment with a slew of desirable properties. It's also fascinating that it was only discovered in 2009 :)
Apropos of nothing in particular, a sentence from Pliny's Natural History:
- "I myself have seen the fleece upon the living animal dyed purple, scarlet, and violet,—a pound and a half of dye being used for each,—just as though they had been produced by Nature in this form, to meet the demands of luxury."
> Because we don't know the dye that was used 3000 years ago, today most omit the blue thread
Were I party to that contract, I (being aware of non-english distinctions) would wear any azure/голубой (sky, not ocean, blue), for:
a) a colour is specified, neither dye nor pigment. (pedantically, it need not even be a reflective colour, presumably something emissive, eg blue EL wire, would be equally acceptable)
b) 15:39 says the colour is meant for the eyes of the wearer, to remind them, so in this case the proper interpretation of "blue" is not even whatever that colour may have been 3'000 years ago, but whatever suggests "tekhelet" to the garment's wearer, today.
(in particular, a tritanope ought to be able to wear suitable grey threads)
Caveat: I have no hebrew, and english has lost its second person singular. Is the second person in the original singular or plural? In the latter case, (b) would need to be amended to match a community, not a personal, interpretation, and the tritanope should then be less free and more frum.
I found a neat photograph [0] of the process of extracting Tyrian purple from Murex snails. There's a remarkable variety of blue pigments that separate out of that, alongside of the famous purple.
(Murex snails being a different hypothesis for the source of the forgotten tekheret dye, separate from the cuttlefish one).
Yep, that and a bunch of ancient Jewish texts mention using blue within religious contexts with spiritual meaning. It's come to be that blue has been considered by Jews as a color that is representative of the Jewish people
[1] https://en.wikipedia.org/wiki/YInMn_Blue