Yes, Cyprea tigris is a variables species. I Have a purple Cyprea tigris
too, and a greenish bottom specimen.
 
Here in Mexico is common to find "blue" dorsum Cyprea caputserpentis,
sometimes polished, other times in natural condition.
 
I have a "melanisthic" cyprea, deep purple dorsum, only with a bit of
blue-grey in the top. Is near to 80 mm. How can i identiffy if this
specimen is a juvenile form of Cyprea tigris, or an adult Cyprea
pantherina ?
 
 
Jorge Mindez
Mexico City