Boy, we have resurrected an old thread huh?!
The purple leaf color is from anthocyanin pigments. Some clones of Doritis pulcherrima have real purple leaves. Well it is not that the leaves are purple as
much as it is an excess of the anthocyanin pigment that causes the purple colored wash. The base color is still green.The darker the pigment, the more vibrant amethyst or purple are the flowers.
But everything about those clones has a purple cast, the root tips are more purple then typical as is the inflorescence! I suspect that this may either be a tetraploid Doritis pulcherrima or a primary hybrid with another purple species. But without knowing its parentage or seeing the plant close up, I can't say for sure.