Was very excited to try this and purchased an open-box M3 15" MBA from BB. I installed Stillcolor 1.1 and confirmed it was working via terminal. I mostly used it with my 32" 4K monitor connected via USB3 -> DisplayPort and running at 3840x2160 60Hz. I tried various color settings with no real difference. I did not try to use any other program to reduce colors (although I may try that later).
The good news is that there was a noticeable improvement - no nausea! The bad news is that there's still something going on that's causing eye-strain/headache albeit to a lesser degree than before. I was able to use the machine to work all day with mild pain and did have lingering effects all evening. I do wonder if I would get used to it, but for now I don't have to so I'm going to return it.
personal eye-strain history:
I tried an M2 15" MBA last year and it caused the usual headaches nausea and returned it (just as I have returned a 16" Intel MBP, other M1 MBP/MBA, any touch bar 15" MBP, and last intel MBA).
I never had any problems with any displays until I purchased an iPhone X which i returned after 2 weeks of trying to get used to it. Since then I've tried every OLED iPhone and they all cause noticeable pain/nausea to a various degrees. I'm currently hanging onto an iPhone 11 (non-Pro with LCD screen) which causes no issues.
I am currently using a late 2013 Intel MBP 15" (pre-touchbar) with zero issues.