People like to play this card of 'I'm fully blonde and white but lol I'm ten Percent African American lol'.
this is the myth.
Firstly, they are few and far between.
Secondly, half of these 'white people' with a 'surprising' amount of black blood look like Jarryd Hayne. Come on.
thirdly, the reason why white people are white is because they lack dominant genes from other races like brown eyes.
Fourthly, don't ignore European history, which were fiercely loyal to the white race and protecting against invaders. It would be unheard of to intermix. Places like Sicily got a little bit of Will Smith in Them but central and Western Europe were protected.