Bandera de la Provincia de Cagayan

In my TL "Filipinas: La Gloriosa y Más Allá", Cagayan is well-known for the naval base of the Royal Philippine Navy in the town of Aparri.  TTL Cagayan included the northernmost towns of Isabela, which are also Ibanag-speaking.

For the flag, it symbolized the flow of Rio Grande de Cagayan (Cagayan River) as it passed the province: Green represented the mountains, yellow represented the Valley and blue the river itself.

100% made in MS Paint, then edited on PhotoScape.

NOTES:
1. The file Castillo héraldico was originally created by Wikipedia Commons user Erlenmeyer.
2. The file "Corona real española" was originally created by Wikipedia Commons user Miguillen.