See Wikipedia.
"Racism consists of both prejudice and discrimination based in social perceptions of biological differences between peoples" ... "In sociology and psychology, some definitions only include consciously malignant forms of discrimination.[4][5] While some consider any assumption that a person's behavior is tied to their racial categorization is inherently racist, regardless of whether the action is intentionally harmful or pejorative, because stereotyping necessarily subordinates individual identity to group identity"
So if you just prefer one group, that's not racist, as far as I can tell. If you make claims about a group's behavior based on race, that's racist.