Red is often associated with supernatural powers and magic in many cultures, and in cartoons, it is often the red-headed hero or character associated with that color that takes the lead.

I would say the idea of blond hair and blue eyes being an ideal has more to do with recent trends than anything. Often, even in older myths and legends, the color meant by "golden haired" was often "true gold" or "reddish-gold" rather than what we know of as "blond", so even then, the hair color of the heroes was often closer to red than yellowish.