royal snails

  A different subspecies of the snail makes a more reddish shade of purple, sometimes called "imperial purple". Imperial purple is considered less valuable than royal purple, but it's still very expensive.   Royal snails are more commonly used to make purple cloth rather than blue cloth because there are more alternative options to make blue cloth than there alternative options for making purple cloth.   Their shells are crushed and ultimately makes a yellow pulpy mess that will turn blue or purple if fermented in the sun. It takes a lot of shells to make a tiny amount of dye, and it takes skillful handling to give the crushed shells the exact right of sun needed to get the desired color.   It is possible to bottle up royal or imperial purple dye and sell it as is (worth more than it's weight in gold), but it is more common to dip undyed garments into the vat of purple mixture while it's fresh. Most high end clothiers find this preferable, and there's a chance of less chance of losing some precious to drying or spoilage if shipped in a bottle.

Real world Hexaplex trunculus are native to a tiny coastal band around the Mediterranean Sea.   Scarterran royal snails, except Scarterra's equivalent to the Mediterranean Sea is much wider. Royal snails can be found where you see elegant purple smears.     The best source for royal snails is the Island of Lunatus (the crescent shaped island on the west side.