Rosaria's cold nature comes from her harsh childhood. When she was young, her village was attacked by bandits, and she was kidnapped. Instead of killing her, the bandits trained her to be one of their own, and she helped them carry out crimes so that she could survive.

Rosaria uses the tall female model. She has ghostly pale gray skin, pale magenta eyes with narrow white pupils, and choppy wine-colored hair cut short in the back with a shoulder-length fringe and some strands of her bangs colored a darker red.

Rosaria is a Sister of the Church of Favonius, which might seem strange considering Rosaria's attitude does not reflect the other Sisters'. However, there's a detailed backstory on...

Yeah in certain lighting she’s definitely gray. I think they may have had trouble conveying a “ghostly pale” character when there are already super pale ‘normal’ characters, and making a character pure white may have looked weirder than the grayish hue they settled on?

Everyone in Genshin is already pale. You don't go grey from paleness. I should know, I'm basically mozzarella.