This is pretty cool. Google Chrome will begin supporting SVG favicons. And because you can embed CSS within SVG, you can use media queries to create dark mode favicons. Smart!
Dark mode favicons — — CSS-Tricks
Archive — Media queries
Note — 2019-08-13
I have now implemented a dark mode for this website. Many operating systems are now offering dark mode as a preference. If you have dark mode switched on, this website now displays in a fetching darker colour scheme.