Blue is a girl's color. It's feminine. A boy wearing blue is saying, "I like girls."
Pink is a boy's color. It's masculine. When a girl wears this, she's saying, "I adore boys."
So is it any wonder that, no matter how unfeminine she acts, even when she punches a noisy, loudmouthed blonde across the Konoha skyline, she's a vulnerable girl at heart?
Or that, no matter how cold he acts to girls, they fall over him like he's the world to them?
It's because he likes a girl. And she loves a boy.