I don't know... using skin tone as measure for attractiveness seems wrong to me. Maybe I am just weird. Whatever happened to judging people by individual merit?
Generally when talking romantic Interest people judge based on looks first and then determine if that's a person they want to get to know better. And people's choices in looks will vary subconsciously depending on what type of relationship they want, potentially also socioeconomic standing, and of course ingrained cultural preferences ....example One night stands (masculine guy) vs stable long term relationship (baby faced guy).....there are a number of studies out there. Everybody has subconscious (sometimes not even subconscious) standards that they judge and categorize people by. I'd like to think I don't bother judging people based just on looks....but also take personality into account.....but I know that's not always true.
added: and I'd never use an appearance mod for a companion...either to make them better looking or change their skin color. To me that would be like asking some friend or person I'm dating to get plastic surgery just to please me.