I have a lot of expired NPS (35mm) that was allegedly cold stored. The colors have not shifted (probably because cold stored) but it has lost a lot of speed. Bracket the exposures. You may find its effective speed is 80 ASA or lower. Also the stuff I have is quite a bit grainier than say Pro S (probably because speed loss affects the smaller grains more). Mine is still very usable but definitely not as good as it would have been when fresh.