[css-color-4] Deprecated and un-deprecated system colors should not be limited to sRGB #8312

As far as I can see, currently in all browsers, the system colors resolve to sRGB.

But going forward that might not be the case, and requiring gamut mapping or clamping to the sRGB gamut seems undesirable.

in Resolving other colors the spec tries to look forwards here, with a somewhat aspirational

Each keyword computes to the corresponding color in its color space. However, such colors must not be altered by 'forced colors mode'.

In contrast the sections on resolving and serializing correspond to current reality, in that the computed value of a system color is an sRGB color which is required to serialize in the legacy, comma-separated rgb() or rgba() form which also uses a 0.0 to 255.0 range, has a minimum 8-bit precision, and thus cannot represent out-of-sRGB-gamut colors.