I have no idea what's involved, so this might be the easiest money ever or way under target, but I'll pay a $5,000 bounty to anyone who can claim commit credit for getting this shipped in chromium.

Just to be clear: All we need is a cli way to do what's already doable by hand by going to chrome://settings/appearance, then Theme, and picking a preset or giving it a color. That then applies to all open instances of Chromium.

@c0d3rguy Actually, chromium --user-data-dir="$(mktemp -d)" --load-extension=~/Work/theme works for new windows. But what I'm looking for is a cli that changes the theme on all existing windows. Just like doing it via the CLI does!