I can't see what the problem is with wondering what colour skin the child of a mixed race couple will have. As I have seen from friends children/grandchildren, it can be so variable, it can be so variable.
We wonder about everything else, what colour the eyes will be, or the hair, will they be as tall as their mothers family or short like their father's. In our case, will they be neurally diverse?
A storm n a tea cup.