working with experimental archaeologist occasionally, I found out an interesting little snippet of info.
natural dyes. the colours can change depending on where the plant/lichen was harvested. a dye made from the same plant can be a totally different shade depending on where you got it.
The origin may well be that as cloth was woven and dyed locally, you could tell where someone was from by the colour their cloth was.
Some of the colours that can be obtained are quite vivid. I've seen a vivid electric purple produced which is remarkably colourfast.