How did you come up with this precise list?

I looked it up on the spec: https://w3c.github.io/csswg-drafts/css-color/#css-system-colors

I can see many more special cases in this rust component:
https://searchfox.org/mozilla-central/source/servo/components/style/values/specified/color.rs#580
(color: -moz-menubartext; is also problematic, so I suspect there is many more case being an issue :/)

Oh right, InspectorUtils.isValidCSSColor("-moz-menubartext") does return true

Unfortunately, I couldn't find any method which would return "accentcolortext" in a list of special predefined colors.

I see that you are trying to align to what chrome does.
I'm wondering if that's the right call... Why would we translate predefined color and not these ones?
But I could understand that these special colors are slightly more like css color variables, which you don't want to change and have the whole UI unified around the original value.

Having said that, given that maintaining the list of all these special colors sounds complicated/impossible, we should probably handle this differently and handle an exception somewhere more nicely?

Yeah. So I think before, color.js had a isValidCSSColor method that was calling InspectorUtils.colorToRGBA and checking that the result was not null, because it does restrict the colors to the ones we can actually properly handle.
I'll probably roll back to a similar version of what we had, only renaming it so it would be like colorHasRgbaTuples

Also I see that with data:text/html,<meta charset=utf8><style>body {color: AccentColor;}</style>Hello we do not display the color in a circle... it would be nice if we could show it.

Yes it would be nice. We'd need to have something on the platform so we can pass a window, as the rendered color might be impacted by light/dark theme.

For some reason it works with data:text/html,<meta charset=utf8><style>body {color: graytext;}</style>Hello... (but clicking on it would also throw can't access property "a", tuple is null)