Annabeth

Seriously...Why the hell was her hair different? it's not that big of a deal, but I find it weird that she went from "blondish" (kid) to brunette, back to blondish.
Sure this could be explained through just dyeing your hair, but what was the purpose?

Why would they have her brunette in the first movie only to retcon it entirely in the second?
EDIT

With some research i figured out why, but it still leaves to question why they left her brunette in the first film.