@fewlines let me ask a silly question. When you open bodyshop (not CAS for those who don't know) do these Sims have a different head tone than body tone when you put these outfits on them in there? I'm curious if we can change your Graphics Rule Sgr. file and set bump mapping to on and some numbers to zero (explain later) if that would help you.
ETA: The following link is about how to fix things blurred in bodyshop etc. However, it just might fix your Sims skin tones, too.
https://www.wikihow.com/Fix-Your-Bodyshop-Settings-in-Sims2