The low night temp purple, you're talking about the petioles specifically? I know leaves and calyxes can turn from that, but petioles? What about branches or stalks? I have seen dying plants with completely purple stalks, it looks like a corpse.
I will concede that it may have a genetic component, but would you say even of the cultivars that do it, the best plants of those cultivars tend to have the least purple petioles? I just think a lot of newbies start seeing purple streaks and get all excited thinking surely it must be some Double Purple Urkle, when really they have not fed anything since it sprouted 26 days ago. Besides that, considering this plant looks like it is planted in some river bottom somewhere, it probably needs some food.