[nullc]

I have astigmatism. White on black or black on white both halo. I think both are equally clear.

It would be somewhat surprising otherwise-- the relevant part of vision for this is linear and should work the same in both directions. Though if the room is so dark that my puples will be dilated then that is obviously going to cause a loss of acuity ... but if that is what the author is going for then the advice should be to not present in a pitch black room.

In a dimmer room I have a small preference for white (or green/amber) on black so that the overall brightness isn't blowing out my vision.

Blue focuses noticeably worse, so I have serious trouble reading things like blue on black or black on blue... esp if the blue is some fancy LED sign or something that uses a shorter wavelength.

I think articles like this that don't support their advice with some kind of study of many people ... is pretty low value because it's too likely to just be repeating the author's own personal preferences and disguising them as research supported Truths.

Safer advice would be: Some people have poor vision, make your text extra big and clear even if you could read something less legible.