You're conflating ethnicity and nationality. Ethnic Greeks have Mediterranean olive-y skin tone, ethnic French, Brits, and Russians are all pale. Nationality is just "people who have the right to reside in nation X", which can include the ethnic Russians whose ancestors have resided there for as long as there has been recorded history, as well as the first-generation immigrants from Zambia. If it's specified that it's ethnic Brits, French, etc, then yes, they'd be pale.

Dark skin, FWIW, is one of those things where it's extremely gradated; someone having slightly darker skin than either of their parents isn't all that remarkable, since there are many genes that add melanocyte production if "on", IIRC. Thus, to produce a significantly-darker-than-parents kid, an improbable quantity of those genes would have to mutate to the "on" position. I really don't think that mutie prejudice got much work with dark-skinned babies. ("This kid is dark; my wife must have cheated on me with the Greekie in the next village!" might have seen more action.)