Should this API allow setting of custom values?

[lukewarlow]

Currently this API is limited to just allowing an override from pre-existing values. At least in the case of color-scheme it's possible that people may want to set a custom colour scheme.

Raised in: https://kilianvalkhof.com/2022/css-html/on-better-browsers-arbitrary-media-queries-and-browser-uis/#overwriting-known-media-queries

Would this be desirable?

How would these values get paired up to browser UA styles for stuff such as scrollbars and form inputs?

Potentially this would be a whole separate proposal on its own that this one could just allow you to set the value from?

[lukewarlow]

See #29 for some examples of sites that would benefit from at least custom colour schemes.