In your anecdote-fueled land of nationalistic mythology, what are the skin colours that the US border agents turn down en masse?

Is it the black folks driving down from Halifax and Montreal? Is it the Asian ancestry-folks with black hair driving down from Vancouver and Richmond? Is it the olive-skinned Greeks or brown-skinned folks with parents from Athens or Mumbai?

Do tell! I have never noticed US border agents screening by skin colour, but I look forward to your report...