[agere_contra]

Having a go at answering my own question (thanks to Wikipedia).

Maybe the blue color is from “Asp of Jerusalem”, the woad plant.

It seems to be a lighter blue than you would get from techelet - and if techelet is made from murex, it wouldn’t be kosher anyway.

[Albion Wilde]

Maybe the blue color is from “Asp of Jerusalem”, the woad plant. It seems to be a lighter blue than you would get from techelet

Did they have red cabbage back then? It always leaves bluish purple stains on the cutting board. This blog, if you scroll all the way down, shows a tablecloth dyed blue from red cabbage:

https://www.remodelista.com/posts/diy-tablecloth-dyed-with-red-cabbage-natural-dyes/