>>106382505
For what I'm doing in those CSS rules, you don't need to use the element picker. I don't know how much CSS you know, but the rules I used are deliberately very broad.

First, we're inverting the colors of the entire document.
html {
filter: invert(100%);
}


Then, we undo the color inversion for img and video so that they're colored as intended.
/* undo what we did with the first html rule */
img {
filter: invert(100%);
}

video {
filter: invert(100%);
}


Attached is how the following page looks with and without that theme using Stylus.
https://en.wikipedia.org/wiki/Rupes_Nigra
https://github.com/openstyles/stylus/