The switch is a real button: it can be reached by keyboard, it announces its state, and its label is read out whether or not you show it on screen. Every scheme that ships was checked for contrast, and the Colours screen shows the contrast ratio of whatever you choose so you can see when a change has gone too far.
For a reader with low vision, pick Bold on the Colours screen: pure black, white text at 21:1, nothing faint anywhere, thick dividing lines, and links in running text underlined so colour is not the only thing marking them.
Motion is dropped for anybody whose system asks for reduced motion.
Still stuck? Ask the developers who wrote it. We aim to reply within one business day.
