Okay, so I've had this problem with one of my families. The mother had skintone 1 and the father had skintone 5 (found here:
http://www.modthesims2.com/showthread.php?t=160572). They had 4 kids (2 boys, 2 girls) and I couldn't figure out for the life of me why they all had skintone 1. I tried quitting without saving again and again, but no matter what I tried, the babies were always pale. I finally gave up on it thinking that somehow the game wasn't recognizing the father's skintone.
Now the kids are grown up and I noticed that the sons have hairy arms. VERY hair arms. Then I remembered that I had downloaded a hairy skintone so I could make Randy from Trailer Park Boys in all of his hairy cheeseburger-gut glory. It seems that what I made the couple in CAS, I must've accidentally chosen that skintone for the mother instead of the regular Maxis skin. Now all of the kids are stuck with it and will probably pass it on to their children. This upsets me.
So now I'm here to ask - what's the easiest way to change a sim's skintone and make it genetic? It's been a little while since I've played, so I'm a little rusty on how things work. Any help is greatly appreciated.