When someone has a blonde moment and their hair is not originally blonde.
Kelly (not born blonde): As I was leaving for work today I couldn't find my keys. I looked everywhere in the store and even asked my friend to help me look for them. When I got to my car, I found them... I locked them in my car.
James: Haha, you had a blonde moment.
Kelly: I'm not blonde, though.
James: My bad, you had a pseudo-blonde moment.