Blonde (with an "e" at the end) is usually used to describe the yellowish-colored hair of a female. 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 (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. When describing a male's yellowish hair or light-colored stained wood, you will more often see blond without the silent "e" at the end. The addition of the "e" in the feminine form of blonde is of course a holdover from its French origin.