Pillow/docs/resources/css/dark.css

/* For black-on-white/transparent images at handbook/text-anchors.html */
body[data-theme="dark"] #text-anchors img {
    filter: invert(1) brightness(0.85) hue-rotate(-60deg);
}
@media (prefers-color-scheme: dark) {
    body[data-theme="auto"] #text-anchors img {
        filter: invert(1) brightness(0.85) hue-rotate(-60deg);
    }
}