Dan:
 
Thanks for the info.
 
There are a number of species in Hawaii that secrete purple dye.  Oliva
paxillus sandwicensis will put out purple dye and stain your hand.  We
laid one on the boat seat cushion and the stain lasted over a year.  Sea
hares Aplysiidae also spurt purple dye in the water when you disturb
them and this seems to be more clearly from being disturbed.
 
Aloha,
 
Wes