The Zeal peeps be dying their hair, yo.

[Fynn]

Schala's hair turned blonde, but so did Terra's, so I don't usually put too much stock in it.

Hmm... Terra's was originally blonde, judging by the artwork, but the sprite artists changed it so that she may be more distinguishable. Whereas Schala was supposed to be blue-haired, if Toriyama's art is anything to go by. You might say the hair change was stylistic, and yet Guile (who was supposed to be Magus, but they scrapped that) still has purple/blue hair. I don't think it's pure stylistic choice.