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She has a long blonde hair. Correct?

He has a long blond hair. Correct?

Would it make any difference if I left out 'a'?

She is a blonde. Her female friend is a blonde too. Correct?

He is a blond. His male friend is a blond too. Correct?

Comments  
anonymousWould it make any difference if I left out 'a'?

You have to leave it out, otherwise they each have only one blond hair.

anonymousShe has a long blonde hair. Correct?He has a long blond hair. Correct?

The difference is not strictly observed, especially with the adjective. I would use "blond" for both, but your version is not wrong.

anonymousShe is a blonde. Her female friend is a blonde too. Correct?He is a blond. His male friend is a blond too. Correct?

I think so. I myself observe the distinction.