Archie of course but I meant in the super hero landscape.
And I think MJ is well known to any comic book fan. She's like the highest profile love interest in comics (because spider man is super popular in general).
And ultimately I disagree. I think her being red is important in the grand scheme. If you can have her be not white and have her be ginger why not do it? You're making a conscious decision not to at that point.
I don't think she's the highest profile love interest in comics either. Jean Grey and Lois Lane seem more well known off the top of my head.
Again, I think you're mixing up the cultural influence of the 90s cartoon with the influence from the books. Which is fine on the surface, when discussing the overall expectation but becomes misleading when you cite it as if the influence is from the source materials reception.
As for why not do it? Because it isn't anymore necessary than her being white. Perhaps she doesn't want to dye her hair and wigs look bad. Maybe red hair actually doesn't suit her? Maybe the creative's on the film don't care about the hair color because it has zero to do with plot, character development/motivation, or anything else that actually determines how the film does?
Or maybe it's because they want to hide that she's MJ for as long as possible and she goes red in a future film?
It can be a conscious choice or not. She really is not a character defined by her hair. She's defined far more by her role in Peter's life, her iconic phrases, and her being beautiful in such a way as to intimidate a young Peter. The specifics beyond that don't matter.