Interesting question. Not all alleles (gene variants) are shared among human strains. Examples of such strain specific genes are really rare , but, as written here:
http://www.nytimes.com/2005/12/16/science/16gene.htmlgenes involved in skin color are part of this group. So, except for albino cases (but being albino is a genetic sickness), it is extremely rare if not impossible that black people generate white one and viceversa.
Is Robert suspicious about something ;)?
However, as written here (
http://news.bbc.co.uk/2/hi/health/4531966.stm ), all genes involved in skin pigmentation excpet one are unknown. So, we don't know if all skin pigmentation genes tend to be strain specific.
