I can confirm about Boron (Orange) and Ceramic (Green), Ruby of course Red.
I also have Black and this one is not transparent like all others, but same shape. This is unknown to me, looks like Beryllium or Aluminum. I've heard that Grace made a limited run of styli (for japan only) after the cartridges were discountinued. Maybe it's one of them.
I also have Black and this one is not transparent like all others, but same shape. This is unknown to me, looks like Beryllium or Aluminum. I've heard that Grace made a limited run of styli (for japan only) after the cartridges were discountinued. Maybe it's one of them.