Sadly, Chrome doesn't support this standard (it has been around for a while and is in HTML4, HTML Living Standard, CSSOM). But you can work around this by JS, see above.
(Edit: It's for things like this that you still want a menu bar for your browser.)
Or alternatively, apply a class to the body tag – e.g. `<body class="high-contrast">` – and declare CSS rules accordingly. Specificity should take care of overriding the 'normal' style rules where needed.
https://developer.mozilla.org/en-US/docs/Web/CSS/Alternative...
I’ve implemented that two ways: having JavaScript pop the alternative attribute off for all but the desired style sheet or simply using a top-level class to modify the relatively few things we were customizing. Back in the day, I used SCSS but CSS Variables have matured to the point where you can do an awful lot that way, too.
The best you can hope for is to forget about it. It's unsatisfying, but less unsatisfying than trying to get back at them or apply "sour grapes" or whatever. None of that works.
The sooner you put your brain on something else, the sooner you'll forget that somebody was a dick to you and got away with it. It sucks, but it's the least worst alternative. Treat it as noise -- which I think is what the OP was trying to say.
I also think it's worth calling it out too though.
How would you go about doing this?
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Edit: to the person who downvoted me for asking a question. Classy.