The CSS color functions lab(), oklab(), lch() and oklch() can contain the special none keyword as a "missing color component" which is treated special when interpolating colors, while simply treated as 0 otherwise (see specification). Axe fails parsing such colors.

color: oklch(0 none none);
color: lch(none 0 none);
color: oklab(0 none none);
color: lab(0 none none);