For the past year or so I've been reading my books with dark mode enabled on an iMac (Books/iBooks). Additionally, I use both Books and Marvin 3 on the iPhone, which also have this feature.
Lately, I've been dabbling with putting together my own epub files, and several of the graphics I want to use are black line drawings with a transparent background. I would like to use CSS
filter: invert() on those so that they'd appear to be white line drawings when dark mode is enabled.
As I experiment, I've been using Calibre's epub editor, which also shows in a dark mode (I don't remember if I've set the preferences for that somewhere or if it defaults).
Will the prefers-color-scheme media query work as it would on a web page? If it does work, how widespread is support for that?
For some of these, I'll be able to find out the answer just by experimenting, but my ability to check my results in different software is limited.