My story takes place in a medieval/fantasy setting. The main part plays out on a locked-off island with a fairly uniform population I'd call Asian to keep this question to the point (look Asian and have those genetics, but of course there is no Asian continent nor culture in that world). They keep to themselves, but of course there is some interaction with the outside world, mainly a nation of seafarers (Caucasian face shape, mostly varying shades of blond, blue or other very low-melanin eyes, white or freckled skin).
What I am looking for is, in a setting that has a very 'pure' racial background (in this case, an island largely locked of from the rest of the world), how would I describe the visual characteristics of children with a mixed background, aka if someone four generations down was rumored to have had intercourse with an 'outsider', what characteristics would they most likely show that people could point at to prove their point? I'd go by simple Mendelian genetics, which is what I learned in school, but the traits most easily describing a human (hair, eye and skin color) are sadly a bit more complicated in their inheritance, which is the core of my problem.
Another question in the same setting: With how melanin (eg. skin/eye/hair color) inheritance goes, how would a condition like albinism affect genetics? Albinism in itself is recessive and would disappear if 'bred' to a healthy partner. But what if the partner is fair skinned, blue-eyed and blond?
In context: There is this young woman, an islander (Asian characteristics), who is an albino. She's carrying the child of one of the seafarers (blond, blue eyed, freckles). Would the dark hair and eye color the albino mother would have had without her condition 'return' in the absence of the albinism, or would the child still be paler than its already light-blond father? And, if she marries an islander, would she be able to pass the child off as his (the man himself is completely informed and supportive), assuming the general public (villagers, gossipers, you know the kind) is not too knowledgeable?
Edit: I deleted the first part because it was misleading. Also edited the last part and added more context to hopefully be more clear.