Description
It looks like the validator does not recognize custom property values with the "background-color" and "fill" properties.
Consider the following example:
CSS:
:root { --primary-color: light-dark(#000,#fff); } ... body { background-color: var(--primary-color); }
or
:root { --primary-color: light-dark(#000,#fff); } ... body { fill: var(--primary-color); }
The validator displays the following:
Value Error : background-color [var(--primary-color)] is not a [background-color] value : [var(--primary-color)]
or
[var(--primary-color)] is not a [fill] value : [var(--primary-color)]
Although, it looks like the "background-color" property is used as an example in the W3C standard.
Standard (CR): https://www.w3.org/TR/css-variables-1/
Standard (Editor's Draft): https://drafts.csswg.org/css-variables/
You can also test the examples with https://tylermorgan.co/ in the validator.