I kinda think that James Patterson has character confusion issues cuz he changes stuff like hair colour A LOT. First he says that Max has blonde hair, then brown, then brown with blonde highlights. So you just have to decide for yourself.
Here is the thing, in the first 3 books she has blonde hair, its says it multiple times. the women who drew the manga has only gotten up to the end of the third book which is coming out in december, because of this she may have only read the first book at the time and she drew her blonde. i believe she is blonde because that is how she started and its like that in the manga and upcoming movie.
If people had actually read the books clearly, the book started that she had brown hair and brown eyes. Later, when they were running from Erasers and they ended up in a city, some people gave them a makeover (yes, Rob Pat actually gave details about this) and gave Max blonde and pink highlights. It states again in the next few books several times that after its grown out, she has brown hair again. In fact, she even has a conversation with Angel (in which Angel states that Max is pretty, and says something along the lines of Max's eyes are like the chocolates they had in France, which Max says "yay my eyes are like barfed up chocolate". And then Angel says something about how in New Hampshire, its legal for Max and Fang to get married, which Max objects to). In this conversation, when Angel says Max is pretty, Max goes something like this in sarcastic way. "Yeah, my hair and eyes are gorgeous. Brown and brown."
I don't think I've ever heard the books say that Bridgett was a brunette, I think she always had auburn hair (hence red head).
I don't know where anyone is getting that she has blonde (or straight) hair other than the makeover in the city. I remember quotes from the book of her saying over and over that she has brown hair. On one of the covers of the books, she has messy curly brown hair, like how she stated. But then on a lot of the other book covers she has straight blonde hair, or, on the manga, curly blonde hair...
Iggy is said to have strawberry blonde hair (which is almost red in tone).