What is the difference between rubio and rubia in Spanish?

You're right to ask! "Rubio" and "rubia" are very similar, but they have a crucial difference:

* Rubio: This is the masculine form of the word, meaning blond (for males).

* Rubia: This is the feminine form of the word, meaning blond (for females).

Here are some examples:

* El niño es rubio. (The boy is blond.)

* La niña es rubia. (The girl is blond.)

So, you would use "rubio" for a male and "rubia" for a female when describing someone's hair color.