Rashi on Leviticus 13:39/רש"י על ויקרא י״ג:ל״ט

1כהות לבנות DULL WHITE — It means that their whiteness is not intense but a dull white.

2בהק A BRIGHTNESS — just like the white which shows itself in the flesh of a ruddy man, who is termed rouge in old French, between his red spots: this is called בהק “brightness” — like a man who is covered with lentil-like spots, when between one lentil-like spot and another the flesh shows bright with a pure brightness.