You are right. It seems to be the tendency of the variety to have dark, almost black, lower leaf pigmentation.
I have two greenhouses and a solarium. I grow Tillandsia in them all. I have pretty much quit growing those "fancy" hybrids though. I now grow mostly those that are actually native to the USA, mostly central and southern Florida. I got interesting in having all the varieties that are native here (and two are native no where else in the world) and I think it is kind of neat to grow them.
