A design in a document

A theme decides how a site looks. But changing a colour shouldn't take a theme of your own, so now a document can do it: a table called Design in the folder profile.

A row per setting; the Dark column is for visitors in dark mode. Fonts are any family on Google Fonts, downloaded once and served from your own site, so visitors' browsers never ask Google. Every value is checked before it reaches the site: one that isn't valid is left out, and the theme's own value stays.

This site's blue is set in its Design document; the table above is an example. All settings are in Design and themes.