Interracial couple kids only have tanned white skin colors after Dec patch.

I don't know anything specific about the code, but from my own experience (out of date though it is) with programming, I'm guessing that a number somewhere is getting truncated or otherwise not calculated incorrectly, and this is the source of the problem.

I mean, IRL, skin color is among the more complicated traits when it comes to genetics because it can be anywhere on the spectrum from the lightest inherited gene to the darkest, so I can see where it's less a case of lack of knowledge as a typo in the coding.