ce} 7 -20.5 100 / none)`);
        test_valid_value(`color`, `color(from color(${colorSpace} 7 -20.5 100 / 40%) ${colorSpace} x y none / alpha)`,             `color(${resultColorSpace} 7 -20.5 none / 0.4)`);
        test_valid_value(`color`, `color(from color(${colorSpace} 7 -20.5 100 / 40%) ${colorSpace} x y z / none)`,                 `color(${resultColorSpace} 7 -20.5 100 / none)`);
        // FIXME: Clarify with spec editors if 'none' should pass through to the constants.
        test_valid_value(`color