Nope, I haven't
FFI-No main character, but none of them have blonde hair anyway.
FFII-Nope, he's a red-head on the NES and like purple or something on the newer versions
FFIII-Once again, no main character, and no blonde sprites.
FFIV-Cecil's hair is white/purple
FFV-Butz hair is brown
FFVI-Terra's hair is green (arguably the "mainest" of characters)
FFVIII-Squall's hair is brown
FFXI-Once again, no main character, but you can be blond if you want.

I won't include any of the "non-FF" FF's, but as you can see, most of the heroes aren't blond at all.