True, talking about the hair of the actors is a bit tedious and petty, but when the most striking visual feature from the MJ we know from the comics is her ruby red hair, and in Spider-Man 2 we were given a ginger wig effort, I think we have right to be a bit miffed.
In Spider-Man 1 she was perfect, the hair was great, and in a lot of shots, it screamed classic MJ, for instance, when she wears the long trench coat after her soap opera audition.
In SM2 she passed for attractive, but it just didn't look like MJ, and some parts got away with it, when she is in Ock's lair, her hair is fine because it is wet and looks darker and when she is in the wedding dress it looks OK because of the lighting, but when she's in the cafe, it is ginger. No two ways about it. I suppose she could have dyed it for her role in the play, and her modelling career, but the previous hair colour was so much better.
So I seriously hope that MJ's hair is back to the way it should be.