La Adivinanza de la Semana

Entramos en la recta final con nuestra última Adivinaza:
 

As you are travelling in the kingdom of Neverland, you come upon a boy and a girl who are dressed exactly alike.

“I’m a boy” says the one with red hair.

“I’m a girl”, says the one with black hair.

If at least one of them is not telling the truth, which is which?

Good Luck!