Canonically, she’s described as having brown hair and brown eyes. (I would love to see more fancasts for a POC Johanna, personally.) 

Seriously, though, why should her hair color make her seem like a stronger person? And I’ve seen so many confessions where people say “Oh, despite the fact that character X is explicitly described as brown-skinned/brown-haired/black-haired/olive-skinned etc., I imagine them as the opposite of that.” WHY? 

(And people who are all, “Oh, Kristen Bell is blonde but I want a ginger” - have you ever heard of hair dye? Wigs? Because by the logic of this confession, Jennifer Lawrence couldn’t play Katniss, she’s blonde. Although I still think they shouldn’t have whitewashed the Seam residents, but that’s a whole ‘nother rant not really related to this confession.)