Carefully reading through here (not the first time), and trying things especially with thoughtful regard to how Stacey's been as thoughtfully reporting, I may have an idea for a way to describe the issues -- which also points to how they may be solved.
The word I think is operable (we're about words here, right?) is: contrast.
Having a few pretty wonderful (and quite variable) problems due to some combination of age, heredity, and degree of aftermath from a pretty heavy situation of diabetes (I'm fine, thank you; it is arrestable), that is a word I can personally well relate to.
That's especially so because there are a myriad of eye and equipment situations which the visual brain works hard to resolve less than clearest information, and when it can't entirely, the perceived result will be a distinct loss of contrast.
This includes focus and retinal issues both, as well as differential between eyes (not seeing identically) and so forth.
A strongly exacerbating factor which often is a problem when Mac people look less than closely at Windows comparability in screen quality, not to say differences in brand setup. I think we've had the basic gamma difference long enough sorted that this is not an issue any more, but it certainly was a big one, especially for images. The differences in font weights, I am not so sure of -- and there Macs have been categorically heavier. Meaning automatic high contrast.
The big difference today may be in screens. When you pay the Apple premium, you get a better screen, typically.
(n. b. to avoid politics:you can know that I carefully went for one of the very first Macs, loved it and upgraded for many years through laptops, newtons, etc.. but left then, over need to interact with corporates in Europe once, ended up with too much expensive software to replace, and Win10 does work. Hence Windows Scrivener, as part of that load.)
If you have an IPS screen, not to say a Retina one, you are greeted every day with a bright, highly colorful, high contrast display -- and all these things over wide angles of viewing. That's what you get on a Mac, or if you pay a considerable premium, may discover you can get if you know to insist, on a Windows machine.
However, many, many Windows laptops and monitors do not have this. They have variations on the TFT technology, because it's cheaper. Then, the contrast is just plain considerably lower to begin with -- and slowly gets worse with age. Much worse, it and color vary so much with viewing angle that on many (all??) laptops with screens of this type, you can't ever get far enough away so that the entire screen will show the same color and contrast. Typically half of the view vertically will be considerably darker or lighter, while greyscale and color values (even solids like icons) fade or bleed away.
I will have to note that for my own eyes, the medical issues just multiply the difficulties on a bad day, as much as I understand how to get the best of the situation.
The difference for software lies in that contrast is something we _can_ improve, by giving options in the application.
No, it isn't quite as simple as it sounds, because of those subtle but all-too-visible differences in the physics results of screen types -- and manufacturers' preferences in presenting them (too bright or too undifferentiated etc. by design choices, mostly for the sales floor).
What can be done in software is what Stacey is asking for, and others have suggested. This is the chance to accommodate a necessary few of Scrivener's appearance factors by means of themable elements.
With care, it could be done with just a few additional settings, it seems.
I started to make a list, out of things Stacey and I have separately suggested, about luminance and colors that could use improving in specific cases, but am thinking of how much designers like to do things themselves.
Also, that way we are much more likely to enjoy a nice and unified look to Scrivener Windows in the sets of settings to be offered. That's important to everyone -- and just so, equally for the needs of overall screen reliability.
Thus after all these thoughts, really it comes back to only one. There should be at least two levels of overall screen contrast -- in unity each. One that looks good on best screens, one that shows up well for normal Windows/laptop screens, and especially for the many actually with present or potential vision issues.
We all don't stay 24, if continuing as best can to think adequately that way
If you can work out colors and grey shades, possibly with some border shapes or thicknesses, for two levels, that will probably make it quite easy to have three levels of contrast, which should do very well.
One for fine screens, one for ordinary, and a further step to harden up the view for the days or hours (sometimes) or longer term need to have comfort in use when vision is not so cooperative.
And each level will look like Scrivener.
It's a concept, anyway. An approach.
Will you see what you can do, given your own chance to think about it?
I think I've heard back positively on that one particular button I couldn't read, and this wider picture is really not a different thing.
And please remember the point I managed to leave out here, the further ability of a 'night' screen. We're helped a lot by recent software like free and wonderful f.lux (https://justgetflux.com/
), so much better than Microsoft's attempt, while many of the eye issues I've alluded to are also affected by blue-white led screen-back illuminators and _their_ contrast problems.
If you make the Scrivener screen 'smooth' in the several contrast modes, which would be your nice design preference, f.lux should go a long ways towards letting you do night screen mode later, and I imagine this should help for operations. In fact I'm looking tonight at this forum, with all its spindly if pretty fonts in a sea of light background, and with your actual wide border shading plus f.lux, it works. Design can work.