I don't think RGB fatigue is an official ailment, but if it ever becomes one, MSI's upcoming Meg X570 Unify motherboard could be a potential cure. It is an "all black beast" based on AMD's X570 chipset for Ryzen.
We only get a teaser shot of the motherboard, with MSI inviting users to "embrace the darkness." It looks like a promising option for an all-black build, and dark-themed cases are easy to come by these days. At the same time, I could also envision this inside an all-white chassis for a sort of tuxedo look.
Embrace the MEG #X570 UNIFY, embrace the darkness, this all black beast is on the way to join your lineup, stay tuned for this big guy!-#MSI pic.twitter.com/7JZC0m0zgSSeptember 19, 2019
Aesthetics aside, the full specs are not yet known, though three reinforced PCI Express x16 slots are clearly visible. There also appears to be onboard power and reset buttons, alongside an LED debug (so there technically is some lighting).
There's no mention of price or when the Meg X570 Unify will launch, only that it is coming soon. Presumably the dragon in the background is not included.