So, recently, when some new babies were born, I noticed that something was off; their parents were an alien and a human, and the human parent always had regular Maxis skin, so I was surprised to see they were all born with what looked like their human parents' skintone. When I checked in SimPe, though, I noticed the skintone listed was not that of either of their parents, but what looks like a custom skintone, which makes no sense since neither parent has it. I'm trying to find the skintone so I can remove it, but I don't know how I'd start.
Ths was the skitone number that came up in SimPE: 2c22a1ce-4751-b705-6b67-2dabb29df63b
I don't know if that's a help or not, but it's the only clue I have.

I'm not sure if this will help since I'm on a mac, but you could search your mod folder for the keyword 'skin tone' or 'default'. I'd also look through your downloads in your launcher as well. Sorry if this advice is useless.