Just a quick clarification, I am going to use the word Criollo instead of Creole. The latter has its own meanings in lots of places that are incompatible with the Spanish system.
The class system in the Spanish colonies has a lot of parts to it, but it is actually relatively easy to understand. All of it is based on two factors. Who were your parents and where were you born. I will go in order of lowest caste to highest. Only for whites did it matter where you were born.
Negro: both parents were of African descent.
Zambo: was a mix between black and indio blood.
Mulato: was a mix between black and white blood.
Pardo: was a mix between white, Indio and African blood.
Indio: both parents came from the native peoples of the Americas.
Mestizo: one parent was Indio and the other was European.
Castizo: was Mestizo but had only a little Indio blood (I'm assuming this meant they just looked really white)
Criollo: was born of two white parents and was born in the Americas.
Peninsulares: was born of two white parents and was born in Europe.
Keep in mind that this system is not based on how you identify, but rather how you are considered by the system. If you were white and born in the colonies then you were a Criollo. They were regularly looked down upon by their peninsulares brethren. It is similar to in the US where white colonials who were primarily born on the colonies were not treated as equals by the English born whites.
If your question was when or why the Criollos started considering themselves Criollos, it wasn't like it was something that they would have been wearing like a badge of honor until the independence wars. It was a identity that was given to them, and it would have been present from birth.
It is one of the reasons that after independence the majority of newly independent nations, all forms of the caste system were erased from law. While racism and colorism was still rampant, and honestly still is, there at least was no institutional system that required racism like there was in the US.
And so you know, this caste system was implemented wherever the Spanish went, so in the Philippines as well.