my black pearl plants are pretty much green with some leaves having green and white. no purple here. the peppers go from black to red.

I'm always fascinated by the unexpected. Assuming you grow more than two Black Pearl, I'd keep an eye on those two to see if they are any different from the green ones when they start producing pods.

Mine only has green on new growth.(Never seen one with any white on it at all.)
My whole plant is dark purple.Pods are round marbles-darker purple/black turn red.Purple pink flowers.
Just like any Black Pearl I've ever seen.
The more sun the darker the plant...

http://davesgarden.com/guides/pf/go/118938/

My Plant=

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Thanks very much for the replies. Since posting yesterday I had occasion to speak with another person who has grown these from seed and she tells me that seeds will germinate with green, purple and mottled seed leaves and they all turn out the same in the end.

Now, I may be wrong, but isn't Black Pearl a hybrid F1? If that is the case, then in the F2, there could be all kinds of possibilities grow out. So, it could be normal to see plants with green leaves and purple leaves and maybe more.

Some Hybrids are stable and the seeds grow true.
Not sure about Black Pearl but I've given people seeds from my plant and they grew true so far.
At least thats what the people I've asked said.