https://www.hunebednieuwscafe.nl/2016/05/wol-verven-op-prehistorische-wijze-experimentje/
-400--> -300 Frisians trading cheese and wool with romans. There are roman diaries which describe the painting of wool with:
- Meekrapplant (Rubia Tinctorum), for red
- Wede (Isatis tinctoria ) for blue
