That's pretty much the very definition of racism. Aesthetic preferences are one thing, but
specifically tying preferences to "inherent" racial qualities is definitely racist on some level. Example:
1. "I don't like girls with frizzy hair."
Not racist.
2. "I don't like black girls."
Definitely racist.
3. "I don't like black girls
because of their frizzy hair." May not be worth grabbing the torches and pitchforks for,
but it is still racist by a baseline standard.
For one, not only are you making assumptions about an entire race and likely tying projection and personal experience to it unnecessarily, but you're also using small numbers of people as spokespeople or representatives for an entire race, aka
stereotyping. Even if you may not consider it offensive or derogatory or whatever in the way that actively subjugating someone to prejudice because of race is, it's absolutely a racist thing to do, even if subtle. "I normally don't like spanish guys, but you're pretty cute," "you're so polite for a Scotsman," "this is the longest I've ever been with a black guy," etc. are
all no-nos. You're absolutely allowed to have
preferences, for example wanting someone with red hair or freckles or glasses or even being tan, but the second you actually tie those qualities to a race, positively
or negatively, it's absolutely racially-charged and by extension racism.