turnsole

noun

1. any of a number of plants whose flowers supposedly turn with the sun, as the sunflower and heliotrope
2. 1. a Mediterranean plant (Chrozophora tinctoria) of the spurge family, yielding a purple or blue dye
   2. this dye

Etymology: ME turnesole < MFr tournesol < It tornasole or Sp tornasol < tornar(e), to turn + sol(e), sun: see Sol