Some of the stereotypes that drive such preferences could, of course, be racist. But it is also true that the factors that attract us to others erotically are not generally matters of simple choice, and the mere presence of a preference "type" does not seem to me to be clear evidence of racism. Some of us prefer tall partners--is this "shortism" because we tend not to prefer short partners?
I think of racism as consisting in beliefs or practices that would deny equal moral, political, or economic rights to members of the targeted race. I don't think anyone has any kind of a right to have me attracted to them as a potential romantic or sex partner, so I can't really see how my preferences in these areas can have the consequences of denying anyone equal rights.
Having said this, I also think that many cultures do lend some support to sexism or to regarding women as second-class citizens. I wouldn't blame a woman from such a culture for having a preference against men of that culture.