For reasons I do not understand, but would like to understand, some sites include "grex" as part of the name of this plant, i.e., "Zygolum Louisendorf grex" instead of the more typical "Zygolum Louisendorf." I don't believe I've ever seen this before. So if you know why people are bothering to write an extra word that would normally be assumed anyway, please leave a comment, 'cause I'm curious.
I appreciate the oddness of the brown/purple color combination, but I don't particularly find it pleasant.1 It's kind of what the Zygo- hybrids do, though, see Zygoneria Adelaide Meadows, Zygopetalum (Kiwi Klassic x Mishima Goddess), Zygopetalum Art[h]ur2 Elle, and Zygopetalum Jumping Jack. (The resemblance to Artur Elle is particularly strong, which makes sense, since Artur Elle is the pollen parent.)
Zygolum Louisendorf = Zygosepalum labiosum x Zygopetalum Artur Elle (Ref.)
Zygosepalum labiosum has a very broad, white labellum (lip), and doesn't look much like Louisendorf at all. In case you were wondering.
2 Some sites have this as "Artur Elle," without the "h," though I included the "h" in the previous post because that was how it was tagged. I didn't feel like spending the time today trying to find out whether or not the "h" belongs there, but I'm guessing that the h-less version is correct, since it's what the International Orchid Registry has. So I'm going h-less for this post.