Pretty sure book 7 is correct.
I dunno about you, but I'm looking at the British version of Book2 on page 35: "On the third landing, a door stood ajar. Harry just caught sight of a pair of bright brown eyes staring at him before it closed with a snap."
If your version says green eyes...document it and auction it off at Christies!
Rhr4eva's answer: I just though I would add that yes, indeed Book 7 is correct. Ginny Weasley has brown eyes.
To whoever asked this: You might be confusing Ginny's eye color with that of Harry Potter's. She sent him a singing valentine through one of Lockhart's "cherubs" that includes, "His eyes are as green as a fresh pickled toad." Ginny's eyes are, in fact, brown.