As a sufferer of visual stress related to dyspraxia and dyslexia, I find tinted glasses and colour overlays extremely helpful for reading. Software overlays, which tint the whole desktop with a colour, are also helpful, and mean I don’t have to wear my very dark and expensive Irlen lenses, which I can’t always afford to renew with my prescription anyway.
On Windows, I use WindowShades. On Mac, I used a similar app that I can’t remember the name of. When I started using Linux, however, there was only one option, Gnome Tint, a GNOME Shell extension. Luckily, I was using GNOME at the time. However, when the project fell out of maintenance without a FOSS licence, I set to re-implementing it as ColorTint in early 2019.
I’m now also working on a new implementation for KDE Plasma, KolorTint, as I’ve recently switched to that for my sins. As my desktop development skills increase, I will try to make a desktop-environment-independent solution, as I want this feature to be as widely available as possible, aiming towards a more accessible GNU/Linux.