Blonde is a yellowish color which can range from honey-toned to almost white. It’s often used as an adjective to describe hair of that color. Marilyn Monroe had famously blonde hair, but only from bleaching — she was naturally a brunette.
Marilyn Monroe's hair was so famous she actually starred in a movie called Gentlemen Prefer Blondes. There the noun blonde is used to mean a person (usually a woman) with light-colored hair and skin. So you can either say, “She is blonde,” or “She is a blonde,” and they mean the same thing — that she has fair hair and skin.
