I've had a few pepper volunteers come up in my seed starts. They're happy little accidents, at least for the time being. Hopefully they wind up producing. Past results have been mixed, but I have the space so I separated them into their own containers.
I have no idea why, but my pepper leaves always turn black under my grow lights. They flip to green once they're outdoors.
What grow light do you use? And what’s your night time temps? It could be too much of one wavelength, or it could be cold night time temps bringing anthocyanins out.
And I think they were commenting on the lime green leaves, they should be a dark green unless I’m off base on peppers.