Hermione hated people with pale skin. She hated ignorance, and how mean and rude people can sometimes be. She hates gluttony, she hates stupidity, she hates uncleanliness, and above all, shehates slackers.
Meet Ron Weasley
Hermione first looked at Ron and found a speck of dirt on his nose. She found it rather annoying. Didn't he bother to bathe?
She later noticed how much his pale skin contrasted with his flaming red hair. She doesn't like pale skin.
Then, in second year, she was especially annoyed with Ron and his personality. He was arrogant, lazy, rude, and a glutton.
She had zero tolerance for stupidity.
In third year, though, she argued with Ron all the time, though she found his appearance to be, surprisingly, improved.
She was absolutely appalled at Ron's inconsiderate feelings and ignorance during the Yule Ball. But she realized she loved that about him.
In fifth year, she noticed how his hair contrasted better with his skin now. It actually looked quite pleasant. He also took better care of his hygine, which added a nice glow to his skin. That, too, looked pleasant.
In sixth year she realized how kind he could actually be, but his lack of common sense led him to miss what was right in front of him.
But, in seventh year, Hermione realized that even though Ron DID have pale skin, he DID have red hair, he CAN BE ignorant and a glutton, and he still is quite a slacker,
She thought he was absoloutley the most perfect person on earth, and that was that.