Why does FF have so many blond main characters?

[Alice]

Or green like Terra. I know the artwork has her blonde, but I've always pictured Terra with green hair. To me, the blonde hair just didn't work.

I never noticed the blond main characters thing. I guess it's one of those minor things you don't really pay attention to.

not that it bothers me, since I prefer to be guys when I play games for some reason.

Hehe...I've always been a fan of playing as a female character. As long as she's not too hyper and happy, anyway.

[Andromeda]

I think it is Japanese design thing, look a lot of Shounen and you'll find that a fair amount of the character have either bright or non-black hair colors. Black hair is the normal hair color for a Japanese person. They fit into society and blend in. If you have a hair color that isn't black you stand out, you're different. It is very noticeable. In some ways it makes you important. Transfer that idea to character design.

In character design you want something memorable and a strong image. The hero has to stand out from the crowd so you can identify them easily. They are the hero of the story, so they are not a normal person anymore. They stand out. And making them stand out involves giving them an appearance that breaks them out of the average and norms. In a lot of cases blonde ends up being that color or orange, which more or less could be seen as blonde.

So that would be why. It's about character design.

[T.G. Oskar]

Or green like Terra. I know the artwork has her blonde, but I've always pictured Terra with green hair. To me, the blonde hair just didn't work.

Second that comment.

In either case, it's mostly a thing of culture. Notice that, essentially, all Japanese have black hair? Black hair is, quite probably, the most common hair color of humans given how abundant it emerges naturally on non-European countries.

Since main characters should have traits that separate them from common people (such as unusual strength, an unusual skill on a thing or two for example), differences in hair color might work.

Now, if you really want a bizarre world: FF Tactics (both the PSX game and the PSP remake) has about 90% of all characters with blonde hair. Only the generic Monks, the generic Onion Knights (on the PSP version), Tietra and Delita, Malak/Marach and Rafa/Rapha have brown hair; there's no blond(e) hair whatsoever.

Blonde hair is chosen since it's a rare natural hair color, builds the feel of non-Hindi Caucasian, it's not as rare as natural red hair, mingles well with green/blue eyes, and separates the main character from the norm.