Baby alien skintone not right.

Yeah, that is definitely a bug. It is possible for a full-blooded alien to be born with human skin as a result of genetic mixing (I've got one in my game) but that doesn't seem like what is going on here. For starters, your mom was straight out of CAS (at least, that's how I interpreted the post). Also, the fact that the baby is wearing the alien onesie indicates to me that they were supposed to have alien skin. (Yes, that is what the alien baby outfit has always looked like. It just looks really, really bad on a human skin tone.)

When my little genetic oddity was born in my game, he wore the standard baby onesie (or rather, a default replacement I had installed) until he became a toddler, at which point he aged into the standard alien diaper. He's been fully alien ever since.

This is him aging up:


And here is he and his (human) twin brother as babies-so identical that I'm pretty sure I labeled them wrong.


So while it is technically possible to have an alien with human skin, it doesn't look like that's what's happening here. There seems to be an issue with genetics as a whole at the moment, so I'm not surprised that aliens are affected too.