I note the comments on the variability of this species geographically.
If I may elaborate, from Desmond Meikle's 'Flora of Cyprus', pp.1292-1293, where he mentions Merton's comments:
"All large populations in Cyprus show wide variations in flower and bract colour, development of sterile bracts, etc."
Meikle goes on:
"In other parts of its, mostly Mediterranean, range the situation is different, particularly with regard to the development of the sterile bracts. In N.W. Africa, for instance, plants without a showy coma are much more frequent than those with, whereas in Turkey and Iran, the violet-topped form is much more common than that without a coma."
Also (I had no idea):
"S. viridis is a strikingly hygrochastic species with the strongly deflexed calyces soon raised to a horizontal position on wetting."