So, when Percy describes Clarisse in The Lightning Thief, she has brown hair. Riordan later changes it to dirty blond hair. Everyone knows that (I think).
But then, on Clarisse La Rue's information, it says that her hair was changed in The Battle of the Labyrinth, when it's actually The Titan's Curse.
"Clarisse pulled off her helmet and marched toward us. A strand of her stringy brown hair was smoldering, but she didn’t seem to notice." -The Sea of Monsters.
"Even Clarisse from the Ares cabin was there, back from her secretive scouting mission. I knew she must’ve had a difficult quest, because she didn’t even try to pulverize me. She had a new scar on her chin, and her dirty blond hair had been cut short and ragged, like someone had attacked it with a pair of safety scissors." -The Titan's Curse.
I don't know if this has been noticed before. And if I'm wrong, sorry for wasting your time. Thanks, and have a nice day on The Riordan Wiki.