The perception of colour happens in the individual, some people are colour blind others tetrachromatic (have more than three receptors)
It therefore is very individual, but yes uniform within certain limits in a percentage of people.
Most of that is only slightly relevant to proving Sigma is better than Kodachrome; sorry for the digression.
I'm not that familiar with Sigma sensors all I know is that they stack just like film, so I suppose they could have a narrower red layer to trim the recordable reds.
I've only played with one sigma and it seemed to have quite a bit of colour bleed, that is take an image of a colour chart and the patches 'bloom' outside the areas into the black surround–that was several years back.
I'm not sure though they would want to build a sensor that mimicked a certain film, that would certainly narrow their appeal as most will want a nice flat linear neutral file to work with that gives many outcomes in software, building in the 'film look' in processed presets a la X-series Fuji.
If we have 'character' in the sensor then I think that make it harder, personally I don't like the colour of Sigma cameras I do like Kodachrome-I'm not sure to me they look the same or similar–I'll have to check out the thread where you post them.
Unless a brave soul wants to post a side by side of sigma and KK 🙂