I'm still around!
I was not able to switch back and have the HD color option work, no. I have an Nvidia 1080 ti card - my previous card was also Nvidia (a 960, to be exact), and all of the color options worked fine with it.
I've confirmed this fix (at least for myself) both on MacOS Mojave and Windows 10, both completely up to date.
As a side note, I don't ever have a monitor plugged into this tower unless I'm actively gaming on it - these screenshots were with no monitor connected at all. It's always worked just fine, including now with this fix, with no monitor attached.
So close...
Your suggestion about changing color depth instantly worked. However, after booting headless, and setting the color depth... I am locked, LOCKED, at 640x480.
...
So. Great. I can SEE my tiny window. But yeah.
