I don't want true colours. I want what I already have, 16-255, to stay reliable in the future.

Is that really optimal? It is already true in that case that your colour schemes do not work for people with opinionated colour settings. Isn't this just relying on a quirk? The point of not using truecolor is to respect the colour preferences of the user.

XKCD 1172? https://xkcd.com/1172/

	▲	johncoltrane 42 minutes ago \| parent [-]
		It has been working for decades and I would rather have it keep working for decades to come. What would be optimal is semantic _styles_ (not colors): - The developer marks the string "XXX" as an error message without even trying to style it. - The platform/user agent/terminal/whatever displays the string in the default style for "error". - The user can adjust the theme of their platform/user agent/terminal/whatever to fit their needs/wants.