The two have similar ingredients: rice, tomatoes, onions, and garlic. The main difference is in the seasoning. Spanish rice is seasoned with saffron threads which impart a sweeter flavor and golden color. If you've had paella, you know what Spanish rice is. Try this recipe for seafood paella by The Mediterranean Dish. Mexican rice is seasoned with cumin, with an earthy, almost nutty flavor, and is usually reddish in color. In fact, you may know Mexican rice as arroz rojo which simply means "red rice".